ALT tags: The HTML tags describing an image that appears when the mouse is rolled over the image on a Web page. Helpful for people who view pages in text-only mode. Some search engines look for keywords in ALT tags.

Backlinks: All the links pointing at a particular web page. Also called inbound links.

Banned: When pages are removed from a search engine's index specifically because the search engine has deemed them to be spamming or violating some type of guidelines.

Boolean search: A search formed by joining simple terms with AND, OR and NOT for the purpose of limiting or qualifying the search. If you search information on salmon fishing in Alaska, and your search also brings back information on trout fishing and diving in Alaska, the Boolean search "salmon AND fishing AND Alaska NOT diving" can narrow your search focus.

Click through: User action that requires clicking on a link in a search engine results page to visit an indexed site. Also refers to clicking on a Web page, banner ad, or email message link.

Click-through Rate: The percentage of those clicking on a link out of the total number who see the link. Also called CTR  

Client: When a computer interacts with a network (e.g., logging on to the Internet) it becomes the "client" of the "server" computer hosting the files on that network.

Cloaking: The hiding of page content. Involves providing one page for a search engine or directory and a different page for other user agents at the same URL. Legitimate method for stopping page thieves from stealing optimized pages, but frowned upon by some search engines resulting in penalties.

Conversion Rate: The relationship between visitors to a web site and actions consider to be a "conversion," such as a sale or request to receive more information. Often expressed as a percentage. If a web site has 50 visitors and 10 of them convert, then the site has a 20 percent conversion rate. Source: Webmaster World Forums 

Comment tags: This HTML tag <!--comments --> is used to insert comments that won't be viewed by users into your pages. Some search engines read comment tags, which can include keyword text and descriptions. Comment tags are also used to hide javascript code from non-compliant browsers.

Cost Per Click: System where an advertiser pays an agreed amount for each click someone makes on a link leading to their web site. Also known as CPC. Source: Webmaster World Forums 

Crawler: A component of a search engine that roams the Web, storing the URLs and indexing the keywords and text of each page encountered. Also referred to as a robot or spider.

Description: Descriptive text summarizing a Web page and displayed with the page title and URL when the page appears as the result of a user query on a search engine or directory. Some search engines use the description in the description meta tag, others generate their own description from text on the page. Directories often use text provided at registration.

Description tags: A meta tag that allows the author to control the text of the summary displayed when the page appears in search engine results. Some search engines respond to this information, others ignore it.

Directory: A server or a collection of servers dedicated to indexing Internet Web pages, returning lists of pages matching user queries. Directories use human editors to review and categorize sites for acceptance and are compiled manually by user submission (examples: Yahoo!, LookSmart).

Domain: A sub-set of Internet addresses. Domains are hierarchical, lower-level domains often refer to specific Web sites within a top-level domain. The distinguishing part of the address appears at the end. Example of top-level domains: .com, .edu, .gov, .org (subdividing addresses into areas of use). There are also numerous geographic top-level domains: .ar, .ca, .fr, .ro (referring to specific countries).

Doorway page: A Web page submitted to individual search engine spiders to meet specific relevancy algorithms. The doorway page presents information to the spider while obscuring it from human viewers. The purpose of doorway pages is to present the spider with the format it needs for optimum rankings while presenting a more appropriate version to human viewers. It's also a way for Webmasters to avoid publicly disclosing placement tactics. The use of doorway pages customizes submission to each individual search engine. Also known as gateway pages, bridge pages, entry pages, portals or portal pages.

Dynamic content: Web page content that changes or is changed automatically based on database content or user information. You can usually spot dynamic sites when the URL ends with .asp, .cfm, .cgi or .shtml, but it's also possible to serve dynamic content with standard static pages (.htm or .html). Many search engines index dynamic content, but some don't if there's a "?" character in the URL.

Document: An item of information that users want to retrieve. It could be a text file, a Web page, a newsgroup posting, a picture, etc.

Heading tags: This HTML tag contains the headings or subtitles visible on a page. Your headings provide a summary of page content and ideally should contain strategic keywords to be read by search engine spiders.

Index: The component of a search engine or directory used for data storage, update and retrieval (i.e., the database).

Indexing: The process of converting a collection of data into a database suitable for easy search and retrieval.

Information Retrieval: The study of systems for indexing, searching, and recalling data, particularly text or other unstructured forms.

Keyword search: A search for documents containing one or more words specified by a user in a search engine text box.

Keywords tag: A meta tag that allows the author to emphasize the importance of strategic words and phrases used within a Web page. Some search engines respond to this information, others ignore it. Don't use quotes around keywords or key phrases.

Link Popularity: Link Popularity refers to the number of sites that link to your web pages from various search engines such as Google, MSN, HotBot, etc. Many search engines use Link Popularity as a factor for determining page rank.

Log File: A file maintained on a server showing where all files accessed are stored. Log file analysis reveals the visitors to your site, where they came from, and which queries were used to access your site. WebTrends is an example of log file analysis software.

Manual Submission: The process of submitting Websites or Web pages to search engines and directories for inclusion in their databases using specific guidelines unique to each index.

Meta Search Engine: A server that passes queries on to many search engines and directories, then summarizes the results. Ask Jeeves, Dogpile, Metacrawler, Metafind and Metasearch are meta search engines.

Meta tags: Information placed in the HTML header of a Web page, providing information that is not visible to browsers. The most common meta tags relevant to search engines are keyword and description tags.

Keyphrase search: A search for documents containing an exact sentence or phrase specified by a user in a search engine text box.

Query: A word, phrase or group of words characterizing the information a user seeks from search engines and directories. The search engine subsequently locates Web pages to match the query.

Referrer: The URL of the Web page from which a visitor came, as indicated by a server's referrer log file. If a visitor comes directly from a search engine listing, the query used to find the page will usually be encoded in the referrer URL, making it possible to see which keywords are bringing in visitors.

Registration: The process of requesting a search engine or directory to index a new Web page or Web site.

Relevance: A subjective measure of how well a document satisfies the user's information need. Ideally, your search tool should retrieve all of the documents relevant to your search. However, this is subjective and difficult to quantify.

Relevancy Algorithm: The method used by search engines and directories to match the keywords in a query with the content of all the Web pages in their database so the Web pages found can be suitably ranked in the query results. Each search engine and directory uses a different algorithm and frequently changes this formula to improve relevancy.

Relevancy: The degree to which a document or Web page provides the information the user is looking for, in terms of user needs.

Re-submission: Repeating the search engine registration process one or more times for the same page or Website. This is regarded with suspicion by search engines because it can be indicative of spamming techniques. Some search engines will de-list sites for repeated re-submission. Others limit the number of submissions of the same page in a 24 hour period. Occasional re-submission of changed pages is usually not a problem.

Robot: Any browser program that follows hypertext links and accesses Web pages but is not directly under human control. Example: search engine spiders, the harvesting software programs that extract e-mail addresses or other data from Web pages.

Search Engine: A search engine is a searchable online database of internet resources. It has several components: search engine software, spider software, an index (database), and a relevancy algorithm (rules for ranking). The search engine software consists of a server or a collection of servers dedicated to indexing Internet Web pages, storing the results and returning lists of pages to match user queries. The spidering software constantly crawls the Web collecting Web page data for the index. The index is a database for storing the data. The relevancy algorithm determines how to rank queries. Examples of major search engines are Google, AOL, MSN and Lycos, etc.. Examples of major directories are Yahoo!, LookSmart and ODP.

Search String: Search strings or terms are the words entered by users into a search engine or directory to locate needed information.

Search Term: A single word or group of words used in a search engine document query. It also refers to the strategic keywords used to optimize Web page content.

Server: A powerful computer that holds data to be shared over a network. Can be used to store critical data for retrieval. A server also acts the communications gateway between many computers connected to it, responding to requests for information from client computers. On the Internet, all Web pages are held on servers. This includes search engine and directory data accessible from the Internet. Typically, the computers running the server software are dedicated to that purpose.

Spamdexing: The alteration or creation of a document with intent to deceive an electronic catalog or filing system. Any technique that increases the potential positioning of a site at the expense of the quality of the search engine's database is regarded as spamdexing, also referred to as spamming or spoofing.

Spider: A component of a search engine that roams the Web, storing the URLs and indexing the keywords and text of each page encountered. Also referred to as a robot or crawler.

Stop Word: Words ignored in a query because they are so commonly used that they can't contribute to relevancy. Includes conjunctions, prepositions, and articles such as and, to and a.

Title: The text contained within HTML title tags, which is not visible to users and not to be confused with headers on the page which are visible and can be similar to the title tag text.

Title tag: An HTML tag with text describing a specific Web page (but not visually displayed on the page). The title tag should contain strategic keywords for the page and be constructed following specific guidelines. The title tag is important because it usually becomes the text link to the page found in search engine listings, and because search engines pay special attention to the title text when indexing pages.

Traffic: The number of visitors to a Web page or Website. Refers to the number of visitors, hits, page accesses, etc., over a given time period. As a general term, it describes data traveling around the Internet.

Unique Visitor: A real visitor to a Website (versus a visit by a search engine robot). Web servers record the IP addresses of each visitor, and this is used to determine the number of real people who have visited a Web site. If someone visits twenty pages within your site, the server will count only one unique visitor and twenty page accesses (the page accesses are all associated with the same IP address).