advertising network: A service where ads are bought centrally through one company, and displayed on multiple Web sites that contract with that company for a share of revenue generated by ads served on their site.
algorithm: The technology that a search engine uses to deliver results to a query. Search engines utilize several algorithms in tandem to deliver a page of search results or keyword-targeted search ads.
click through rate (CTR): The rate (expressed in a percentage) at which users click on an ad. This is calculated by dividing the total number of clicks by the total number of ad impressions. CTR is an important metric for Internet marketers to measure the performance of an ad campaign.
content network: A group of Web sites that agree to show ads on their site, served by an ad network, in exchange for a share of the revenue generated by those ads. For example: Google AdSense or the Yahoo Publisher Network.
cost per action (CPA): A form of advertising where payment is dependent upon an action that a user performs as a result of the ad. The action could be making a purchase, signing up for a newsletter, or asking for a follow-up call. An advertiser pays a set fee to the publisher based on the number of visitors who take action. Many affiliate programs use the CPA model.
cost per click (CPC): Also called Pay per Click (PPC). A performance-based advertising model where the advertiser pays a set fee for every click on an ad. The majority of text ads sold by search engines are billed under the CPC model.
cost per thousand (CPM): An ad model that charges advertisers every time an ad is displayed to a user, whether the user clicks on the ad or not. The fee is based on every 1,000 ad impressions (M is the Roman numeral for 1,000). Most display ads, such as banner ads, are sold by CPM.
geo-targeting: Delivery of ads specific to the geographic location of the searcher. Geo-targeting allows the advertiser to specify where ads will or won't be shown based on the searcher's location, enabling more localized and personalized results.
Googlebot: Google uses several user-agents to crawl and index content in the Google.com search engine. Googlebot describes all Google spiders. All Google bots begin with "Googlebot"; for example, Googlebot-Mobile: crawls pages for Google's mobile index; Googlebot-Image: crawls pages for Google's image index.
inbound link: An inbound link is an hyperlink to a particular Web page from an outside site, bringing traffic to that Web page. Inbound links are an important element that most search engine algorithms use to measure the popularity of a Web page.
keyword: A word or phrase entered into a search engine in an effort to get the search engine to return matching and relevant results. Many Web sites offer advertising targeted by keywords, so an ad will only show when a specific keyword is entered.
link bait: Editorial content, often sensational in nature, posted on a Web page and submitted to social media sites in hopes of building inbound links from other sites. Or, as Matt Cutts of Google says, "something interesting enough to catch people's attention."
link building: The process of getting quality Web sites to link to your Web site, in order to improve search engine rankings. Link building techniques can include buying links, reciprocal linking, or entering barter arrangements.
meta tags: Information placed in the HTML header of a Web page, providing information that is not visible to browsers, but can be used in varying degrees by search engines to index a page. Common meta tags used in search engine marketing are title, description, and keyword tags.
quality score: A score assigned by search engines that is calculated by measuring an ad's clickthrough rate, analyzing the relevance of the landing page, and considering other factors used to determine the quality of a site and reward those of higher quality with top placement and lower bid requirements. Some factors that make up a quality score are historical keyword performance, the quality of an ad's landing page, and other undisclosed attributes. All of the major search engines now use some form of quality score in their search ad algorithm.
search advertising: Also called Paid Search. An advertiser bids for the chance to have their ad display when a user searches for a given keyword. These are usually text ads, which are displayed above or to the right of the algorithmic (organic) search results. Most search ads are sold by the PPC model, where the advertiser pays only when the user clicks on the ad or text link.
search engine marketing (SEM): The process of building and marketing a site with the goal of improving its position in search engine results. SEM includes both search engine optimization (SEO) and search advertising, or paid search.
search engine optimization (SEO): The process of making a site and its content highly relevant for both search engines and searchers. SEO includes technical tasks to make it easier for search engines to find and index a site for the appropriate keywords, as well as marketing-focused tasks to make a site more appealing to users. Successful search marketing helps a site gain top positioning for relevant words and phrases.
search engine results pages (SERPs): The page searchers see after they've entered their query into the search box. This page lists several Web pages related to the searcher's query, sorted by relevance. Increasingly, search engines are returning blended search results, which include images, videos, and results from specialty databases on their SERPs.
social media: A category of sites that is based on user participation and user-generated content. They include social networking sites like LinkedIn or Facebook, social bookmarking sites like Del.icio.us, social news sites like Digg or Reddit, and other sites that are centered on user interaction.
spider: A search engine spider is a program that crawls the Web, visiting Web pages to collect information to add to or update a search engine's index. The major search engines on the Web all have such a program, which is also known as a "crawler" or a "bot."
title tag: An HTML meta tag with text describing a specific Web page. The title tag should contain strategic keywords for the page, since many search engines pay special attention to the title text when indexing pages. The title tag should also make sense to humans, since it is usually the text link to the page displayed in search engine results.
universal search: Also known as blended, or federated search results, universal search pulls data from multiple databases to display on the same page. Results can include images, videos, and results from specialty databases like maps and local information, product information, or news stories.
Web 2.0: A term that refers to a supposed second generation of Internet-based services. These usually include tools that let people collaborate and share information online, such as social networking sites, wikis, communication tools, and folksonomies.