Here is what I believe to be a beginner's glossary to Search engine and Web terms. I must have of course omitted a few key terms but if you post them in the comments section I will add them. Don't forget you can use the "define:your term"function in Google!

• Absolute Unique Visitors - The number of unique individuals who've come to your site in a given time period. So, if I come to your site 20 times in a week, I still only count as a single unique visitor. This statistic is important because it tells you your reach, or the total size of the audience coming to your site.
• Algorithm - Step-by-step procedure for carrying out a mathematical computation or a transformation of data, usually used in reference to work performed by a computer.
• CSS - A W3C recommended language for defining style (such as font, size, color, spacing, etc.) for web documents. Very search engine friendly.
• Code – aka Markup - The background code that runs a web site. As well as HTML & XHTML, this can include, CSS, JavaScript, ASP, PHP, JSP, Coldfusion and more.
• Dead link - An Internet link which does not lead to a page or site. This usually occurs when a server is down, the page has moved, or it no longer exists. You do not want dead links on your website – there are free tools to check if your site is pointing to dead links.
• Directory - directories are built from submissions made by website owners, and generally arrange site listings hierarchically.
• Domain - A sub-set of Internet addresses. Domains are hierarchical, and lower-level domains often refer to particular web sites within a top-level domain. The most significant part of the address comes at the end - typical top-level domains are .com, .com.au , .net, .edu, .gov, .org.
• Dynamic html - web pages generated on demand by data in databases or using similar technology. Can create ranking problems because a search engine's spider may not retrieve relevant content.
• Frames - Some sites have pages that are made up of multiple HTML pages. Typically the navigation will be on one page and the content on another. You can tell if a website is built in Frames by looking at the source code and also if the website address is always the same for each page. Frames are an old technique and are NOT search engine friendly.
• Google Adsense - Contextual advertising by Google. Website publishers earn a portion of the advertising revenue for placing Google sponsored links on their site.
• Google Adwords - This is the Pay Per Click advertising program offered by Google.
• Hidden text - Text that is visible to the search engine spiders but not to site visitors. Used to add extra keywords in the page without actually adding content to a site. Most search engines will penalise Web sites which use hidden text. Do NOT use this practice!
• Home page - The main page of a Web site. Generally called index.html HTML (HyperText Markup Language) - The coding language that all Web sites use to exist on the Internet. Check www.w3c.org
• Hyperlinks - Hyperlinks are used to link one or more documents together.
• Impression - A single display of an online advertisement.
• Inbound link – aka backlinks - Links that direct users to another Web site. When a user arrives at a site from another site, that link is known as an inbound link. You need a reasonable amount of great quality inbound links to increase your search engine rankings.
• Invisible text - using a font color the same or close to the color of the background of a page, in an attempt to allow the content to be indexed by search engines while not being visible to humans. To search engines, this is spam.
• Keyword density - Keyword density is the ratio of a keyword or key phrases to the total number of words on that page.
• Keyword frequency - Keyword frequency is the number of times keywords occur in the text on a given page. Search engines want to see more than one repetition of a keyword in your text to make sure it's not an isolated case.
• Keyword meta tag - Due to abuse by many Web sites in the past, search engines have reduced the importance of the keywords meta tag when ranking a Web page for keyword relevance. Many have actually decided to not consider the keywords tag altogether. While it has reduced in significance, it is still a relatively important meta tag to include in your Web pages.
• Keyword phrase - A phrase used to find pages when conducting a search.
• Keyword research / keyword analysis - Researching the most relative and popular keywords for a given site.
• Keyword Spamming - Deliberate repetition of keywords in a page by using invisible or tiny text to increase keyword density. This is banned by search engines.
• Keyword - A word used to find pages when conducting a search.
• Link analysis - a measure of the quality and relevance of the set of links pointing to a given site; contrast with link popularity.
• Link baiting - To create something that naturally attract backlinks for your web page by getting people to talk about it, discussing it on forums, blogging about it, posting it on social bookmarking sites and linking to it from their sites.
• Link Farms - sites created and maintained solely for the purpose of constructing links between member sites. Should be avoided as a violation of most search engines' policies; their use won't build your site's link popularity, and may result in a ranking penalty.
• Link popularity - Search engines often use link popularity as part of their ranking criterion. In simple terms, link popularity is the measurement of the number of other Web sites that include a link to your Web site on theirs. Each search engine, depending on their specific algorithms, determines it differently.
• META tag - html tag in the header section of a web page, intended to offer content to search engines. Among them are the keyword and description tags, but these days most true search engines de-emphasise or completely ignore meta tags.
• Mirror sites - Sites designed as duplicates of an original site, but are hosted on a different server. Link cloaking and doorway pages, the creation of mirror sites is a recognized spam tactic and violators will be penalised by many of the major search engines.
• ODP- Open Directory Project: The largest human edited directory on the Internet. The Open Directory provides listings for free but only for qualified sites and because editors are volunteers, wait times can be lengthy.
• Outbound link - A link to a site outside of your own.
• Page Rank - A numerical rating of a site developed by Google as part of it's algorithms for determining search engine listings.
• Page Views - tells you how many pages of your site are viewed in a given period. If I come to your site 20 times in a week, viewing 3 pages each time, I count as 60 page views. Page views are an indication of just how interested people are in your site. A high ratio of page views to visits likely means an interested audience.
• PPC - Pay Per Click. This is an advertising option in which the advertiser has typically a small textual ad on a search engine site and pays only if a user clicks on the link in the ad.
• Reciprocal link - An exchange of links between two sites. Not a good technique for SEO.
• Relevancy - how closely related a particular page is to the search term requested.
• Search engine - A search engine is a database system designed to index and categorise internet addresses, otherwise known as URLs (for example, http://www.untanglemyweb.com).
• Search engine marketing (SEM) - encompasses several forms of marketing products and services on the Internet through management of information presented by search engines and directories. Example: Pay Per Click.
• Search engine optimisation (SEO) - These are the techniques used to improve a Web page's results in a search. You do not need to pay the search engines for this.
• Search engine positioning - the process of managing a page or site's positioning in the search engines.
• SERP - A "search engine results page," the page of site listings that a search engine returns in response to a user's entry of a search query. Spam: as it applies to search engines, any attempt to submit or place deceptive information, or to "trick" the search engine into placing a page in an inaccurate position.
• Spider – aka crawlers or robots - A software program used by search engines to crawl the Web, storing URLs and indexing the keywords and text of pages. Spiders are also referred to as crawlers or robots.
• Traffic - The actual visitors to a Web page or Web site.
• URL - The Uniform Resource Locator is used to specify the address of Web sites and Web pages.
• Visits - The number of times people open your site in their browser. If I come to your site 20 times in a week, I count as 20 visits. This is important, too - a high ratio of visits to visitors means you've got a loyal audience.
• Word stemming - a practice used to some search engines in which searches will return results for words based upon a particular stem. For example, a search for "develop" might return pages containing the words "development" or "developer."