The WordPress Codex is intended to be an encyclopedia of WordPress knowledge.
Founded to revitalize the collaborative documentation efforts for WordPress that began to wane on the previous document site (the defunct wiki.wordpress.org), it takes its name from codex (latin for book), the first invented form of paged volume we recognize as a book, immediately succeeding the scroll as a means to record writing.
One reason for the decline in use of the previous documentation was a certain user-unfriendliness of the tool used. We’ve chosen a new one for Codex called MediaWiki — developed by the Wikipedia team — which we think greatly enhances the user experience. Another issue with the previous wiki was in the organization of content: it developed without a structure, making it extremely difficult for users to find information. We hope to alleviate this in the WordPress Codex by implementing guidelines for its organization and by keeping a devoted group of moderators to enforce these guidelines.