In order to clarify the search arena, it is necessary to define the different kinds of search entities: search systems, search sites, search directories. Search systems and search sites are also called search engines and one will seldom hear any other term in use. Nevertheless, it is very important to know the differences between them to understand the relationships between the search engines.
A search system is an organization that possesses a combination of software, hardware, and people that is used to index or categorize Web sites. Search systems build the index or directory that users search through at a search site (Kent 2004, 12). Inktomi, for example, is purely a search system. It constructs a search index and feeds those results to other search engines. Inktomi does not have a search function on its website, which means that it is not a search site. Other search systems include Google, Yahoo and Ask Jeeves.
A search site is any web site that provides search results to users. Search sites do not need to compile their own database with a unique algorithm, but they can use the results of other search systems that feed them. AOL Search is an example of a search site that does not have its own search system. Google feeds AOL Search with organic and paid results. Google, on the other hand is an example of a search site that uses its own search system to return results. Some search sites compile results from several search systems. These search engines are called meta-search engines.
Search directories are searchable subject guides organized by topical subject or geographical region. Search directories consist of web sites that have been reviewed and compiled by human editors. (Boswell.) Many search directories, like the Open Directory Project (ODP) and Skaffe are also search systems and search sites, i.e. they build their own search directory and present results to users on their site.