A search engine is a program designed to help find information stored on a computer system such as the World Wide Web, or a personal computer. The search engine allows one to ask for content meeting specific criteria (typically those containing a given word or phrase) and retrieving a list of references that match those criteria. Search engines use regularly updated indexes to operate quickly and efficiently.

Search engine optimization is a set of methodologies aimed at improving the visibility of a website in search engine listings. The term also refers to an industry of consultants that carry out optimization projects on behalf of client sites.

A hyperlink, or simply a link, is a reference in a hypertext document to another document or other resource. As such it would be similar to a citation in literature. However, combined with a data network and suitable access protocol, it can be used to fetch the resource referenced. This can then be saved, viewed, or displayed as part of the referencing document.