Acquisition: The point at which a visitor becomes a qualified lead/customer. Generally this is the point where the visitor buys a product, provides contact details or indicates an interest in the product.

Click Through Rate (CTR): The percentage of those clicking on a link divided by the total number who see the link.

Conversion Rate: The relationship between visitors to a web site and actions considered to be a ‘conversion’, such as a sale or request to receive more information. Often expressed as a percentage.

Cost Per Action (CPA): An online advertising payment model in which payment is based solely on qualifying actions such as sales or registrations.

Cost Per Click (CPC) or Pay Per Click (PPC): An online advertising payment model in which an advertiser pays an agreed amount for each click to their web site.

Cost Per Lead (CPL): The total cost of an advertising campaign divided by the resulting number of new leads.

Cost Per Thousand (CPM): System where an advertiser pays an agreed amount for the number of times their ad is seen by a consumer, regardless of the consumer's subsequent action.

Directory: Lists of websites, categorized and organized by topic such as products or services. Each directory listing contains short, descriptive information about the site. Unlike spidering the web to index content, directories are compiled by human editors who approve listings.

Keyword(s): Word(s) that web users type into a search query box to find specific content.

Search Engine Optimization (SEO): The process of choosing targeted keyword phrases related to a site, and ensuring that the site places well when those keyword phrases are part of a web search.

Search Engine Marketing (SEM): A form of online marketing that makes a site and its content highly relevant for both search engines and searchers. Successful search marketing helps a site gain top positioning for relevant words and phrases.