SEO Terminology

Below is a list of terms that come up every now and again while promoting a web site for beter search engine placement. Some are more technical than others, however a general understanding can go along way when making critical decisions.

Above the fold: "Above the fold" comes from newspaper advertising -- where the top story was placed "above the fold". On the web "above the fold" refers to the viewable content in the browser that is viewable without having to scroll the window down.
Adwords: Google's advertising network, where advertisers can pay a certain amount for each click (see CPC). You can setup how much you want to spend per day on advertising, and create several custom text ads, which will rotate through the search engine results and/or content pages as well (see Adsense),
Adsense: Google's money making program for webmasters, where you can show targeted, relevant ads on your web sites. Commission is paid out at 50% of the total revenue for a click. Signup is free, and only requires a tax payer id, or social security number. Google will then write you a check each month, or as soon as you earn over $100. See Google Adsense (http://www.google.com/adsense)
Apache: One of the most popular open source web servers on the internet. More info at apache.org (http://www.apache.org)
API: API stands for Application Program Interface. In it's simplest definition, an API is a means by which one program can exchange information with another program via it's API.
API Key: An API key is typically a unique id given upon registration for usage of an API, such as Google's API. The key identifies the user, and in Google's case, serves as a means of tracking the user, as well as limiting the user to 1,000 queries per day.
Backlink: Backlink (also referred to as an "incoming link" or "reciprocal link") refers to the number of web pages in Google (and other engines), that have a link to your site. For example, you can type "link:www.organicseo.org (http://tinyurl.com/7safk)" in Google to determine how many pages link to your site, which inturn will have a direct effect on your ranking in the SERPs.
Blog: Simply put, a blog (or weblog) is an online diary or journal. There are many options out there for bloggers, including blogger.com (http://www.blogger.com) and others, that allow for a user to update their blog on a daily basis. Blogs usually revolve around a topic or interest that is held by the owner, although they can also be rants or other informative postings. Because of the dynamic nature of blogs, Googlebot tends to visit these sites more often since the content is updated regularly.
Clickthrough: A clickthrough (or clickthru) refers to the act of a visitor actually clicking on an advertisement and following through to the advertiser's web site.
CPA: CPA is short for "Cost Per Acquisition". Simply put, it means you get paid for every sale you generate promoting a product. So you would advertise a product whichever way you would choose: banner, text ad, link, etc. For every sale that your marketing generates, you earn a percentage, typically 40-50%. In theory, this allows for you to make more money then charging a flat CPM rate for advertising.
CPC: CPC (Cost Per Click) refers to the amount of money an advertiser will pay each time someone clicks on their ad. For example, the word "casino" in Google Adwords may cost an advertiser upwards of $12 per click.
CPM: CPM stands for Cost Per Million, which used to be used to describe the amount of money paid for 1 million page impressions. However, since it was determined in the dotcom days that impressions could easily be faked, the industry opted to use CPM to refer to Cost Per Thousand clickthroughs.
CPQ(L): Cost Per Qualified Lead (CPQL) refers to the cost of your advertising campaign compared to the advertising spent divided by the number of "qualified" referals. If you spent $100 and receive 4 qualifed leads, then your CPQ is $25. Typically, the CTR rate is much higher than the CPQ rate, as not everyone who clicks on your ad will end up qualifying as a potential client or customer.
Critical Mass: Critical mass is used to describe the state of an interactive site, in which it's users start to really contribute and visit the site on a regular basis. It's often used to describe the early stage of an online forum or community.
CSS: CSS stands for Cascading Style Sheets, and is used to seperate content from presentation in a web page. Typically contained within a seperate external file (ie - style.css), you can control the look of a page, from font sizes and colors, to positioning of elements on the web page. For more info, see W3 Schools (http://www.w3schools.com/css/default.asp)
CTR: Click Through Rate (CTR) refers to the total number of impressions divided by the total number of clickthrus. For example, if you had 10,000 banner impressions that yielded 200 clicks on your ad, you would have a CTR of 2%. It's difficult to say what a good clickthru rate is, as it varies from site and product. Typically, 2-4% is considered pretty good - the more targeted your ads are, the greater chance you'll have of increasing your clickthru rate.
Deep Crawl: A deep crawl is when a spider, such as Googlebot crawls the entire web site. Typically, Googlebot will index only the first page (or home page) the first time it encounters a new site not already in it's index. It can take up to 1 month for Googlebot to return and do a deep crawl, following all the interlinked pages on a particular web site.
Directory: A directory is simply a web site, which maintains a collection of other web sites that are submitted by people, categorized by content. A listing in a directory usually contains a link, with a descriptive title, and a brief description of the web site listed. The most well known free directory is Dmoz (http://www.dmoz.org). There are many, many directories on the web which are big and small alike, some are broad in classification, like Dmoz, while others are dedicated to specific topics, for example a "business directory". Your best bet is to submit your site to these directories, rather than search engines.
Google: The world's most successful search engine, Google (http://www.google.com) has grown by leaps and bounds in the last several years, doubling their number of indexed pages to over 8 billion. It's the most sought after search engine for placement by SEO masters.
Googlebot: One of the more well known spiders owned and operating by Google (http://www.google.com), which crawl the web, indexing pages.
Googlism: Google offers several little known tricks or functions you can type into the search field, also known as "googlisms" for retrieving information about a web site. Ranging from the number of backlinks, to the number of pages indexed. See Googlisms for more info.
HTML: HTML stands for Hyper Text Markup Language. HTML is the standardized way of laying out the content in a web page. More recently, XHTML has been gaining ground over HTML as a more structured markup language. See HTML on Wikipedia.org (http://en.wikipedia.org/wiki/HTML)
Inbound Links: See Backlinks
Index: This refers to the database of a search engine company that stores all the content on the web it's spiders have crawled. The spider's actions are commonly refered to as "indexing the web".
IP Address: The IP (Internet Protocol) address is a unique number every computer on a network has. Think of it as a phone number for your computer, used to identify your ISP and your computer. People engauging is malicious activities have often been traced by their IP number. See Internet Protocal (http://en.wikipedia.org/wiki/Internet_Protocol) on Wikipedia.org for more info.
ISP: ISP stnnds for Internet Service Provider. An ISP can be the means you use to connect to the Internet (examples include Comcast, SBC Dsl, or AOL), or even the company from which your purchase your web server or hosting provider.
Log: A log file refers the a file that is created by a program as a means of tracking what is happening during the usage of that program. For SEO, your most important tool is your web server's log file. It will provide you with information about your visitors, ranging from pages accessed and times, to which search phrases and search engines they are using. See statistics.
MFA: Made For Adsense (MFA), in reference to questionably spammy web sites that are made for the sole intention of converting Google Adsense ads.
Open Source: Open source refers to a methodology of software development. It's strength lies in the act of giving away a software package for free, including it's source code which is available for anyone to peruse and improve. The software can be re-distributed among licenses such as the GPL (http://en.wikipedia.org/wiki/GPL), which requires that you can modify the code and re-distribute as long as those same rights are also passed along. Many open source projects are maintained by a vast community of volunteer software developers. Projects of note are FireFox (http://www.mozilla.org) and Linux (http://www.linux.org).
PageRank: Google PageRank refers to the number between 1 and 10 (10 being the highest) that Google assigns a page. You can download the Google Toolbar (http://toolbar.google.com) for Internet Explorer or GoogleBar w/PageRank (http://www.prgooglebar.org) for FireFox (http://www.mozilla.org)
Proxy Server: A proxy server is a server connected to the internet that will forward a request for you to the final destination, usually HTTP (http://en.wikipedia.org/wiki/Http). The reason people use a proxy server is to cover up the originator's IP address. You can send your request through a second proxy server, or even a third server, and the results of the request are forwarded back through the servers to you. Thus querying google.com would make it look like you were coming from the proxy server's ip address, not your own. Nefarious tools use proxy servers, as well as people who want to remain anonymous. Typical uses are for scraping web sites.
Reciprocal Links: See Backlinks
robots.txt: The robots.txt is a text file which you can place anywhere on your server (within htdocs), to limit access by spiders to a particular directory. robots.txt is only used by spiders that support it. Screen scraping commonly does not look for a robots.txt file.
Root: Root describes the "superuser" on a Linux or Unix-based systems. Usually only the administrators of the server have access to this account. It allows full control of everything on the server. Sometimes it comes up in SEO because certain tweaks are necessary on the server, for example URL rewriting in Apache.
SEO: SEO is an acronym commonly used to abbreviate "Search Engine Optimization". The act of optimizing a web site for higher rankings in search engines.
Search Engine: A search engine refers to a web site that is dedicated to indexing the web via spiders, providing it's users with a searchable database of content from the web. Search engines of note are Google (http://www.google.com), Yahoo! (http://search.yahoo.com/), and MSN (http://search.msn.com).
SERPs: Search Engine Result Placements (SERPs) is commonly used to describe how well you're doing in the search engines for a particular phrase. For example, one might say "I'm ranking #2 for the phrase 'seo wiki' in Google and Yahoo SERPs."
Session ID: A session id is a unique identifier assigned to a visitor, usually as a parameter in the url ("/index.php?sid=234jiod08ekjd08pje") or as a cookie. Spiders tend to get caught up in sites with session ids, and are now actively weeding out sites that use session ids in the url.
Scraping: Scraping refers to the act of parsing results from a web site in an automated process. Typically, this can be a Perl script using LWP::UserAgent and HTTP::Request modules to grab the content from a server. It's a somewhat questionable practice to scrape web sites, unless you have permission from the copyright owner beforehand.
Spam: Most people think of spam as unsolicited email. Spam can also be used as unsolicited postings on blogs, forums and guestbooks. This is quite common if you have a free link section on your web site, or a forum in which people can register and post links on a web site. Counter measures include visual confirmation in order to post, so as to keep people from writing automated scripts (non-organic methods) that will look for exploitable software.
Spider: Also known as "robots", "bots", or "crawlers". These are programs search engines use to index the web. They typically start at a location, or many, and follow all the links on a page it's indexing. As they go about their crawling, they undoubtedly find new pages and web sites, and continue to follow all those links as well. Eventually building up a huge database that contains all the pages and sites indexed by the spider. Googlebot is one example of a spider, which crawls the web 24/7 indexing the internet for the Google search engine.
Visual Confirmation: Visual confirmation refers to a counter measure that can be implemented on a submission form to discourage automated spam submissions. Typically it consists of an image with a set of multi-case letters or word. The person then needs to enter the letter/number sequence from the image into a form field in order to continue. This is common practice on forums and blogs, which would stop automated scripts from submitting and getting a free link.
Web Server: A web server is a computer that is set up to serve web pages to clients (your visitors). In other words, it's the computer (including it's web serving software, like Apache), that is hosted at your ISP's location and handles all requests for your web site. See Web Server (http://en.wikipedia.org/wiki/Web_server) on Wikipedia for more detailed info.
Wiki: A Wiki is a web site software package that allows visitors to edit the content of the pages. This site uses MediwWiki (http://www.mediawiki.org). Another notable wiki is Wikipedia (http://www.wikipedia.org), an online encyclopedia edited by the internet community. There are many wiki packages available, including WordPress (http://www.wordpress.org).
XHTML: XHTML refers to eXtensible Hyper Text Markup Language, and is a more strict form of it's predecessor, HTML. See XHTML on Wikipedia.org (http://en.wikipedia.org/wiki/XHTML)
XML: XML is short for eXtensible Markup Language. In layman's terms, XML is a language used to describe data or content. XML is advantageous because it serves as a parsable structured form of markup, unlike HTML. XML is only considered "valid" when the tags are nested and closed properly. See XML on Wikipedia.org (http://en.wikipedia.org/wiki/XML).