Indexing is the process of lexical Web page content analysis by a search system robot, detection of new pages, changes in the existing systems and putting of this information in a search server database.
Usually indexing occurs in two stages: detection of the link to the page and its putting on a queue for indexing and directly indexing of the page content and a record of this compressed information to an index of a search system. At this point contents of a Web page of links to other documents are searched.
The indexing process ought to be distinguished from the process of ranking. First is collection of data, second is ordering of the page position in the index.