Extensions are features and add-ons developed for MediaWiki, the software platform that Wikia runs on. They are designed by third-party developers (that is to say, not Wikia or MediaWiki staff) for the purpose of either expanding the function of a wiki or overriding a built-in MediaWiki feature for customization purposes.
See Category:Extensions for help pages on Wikia Help. Note this article may not be completely up to date.
Grants users with the appropriate permission the ability to check user's IP addresses and other information (This is generally a staff-only tool. A few wikis have a few users with this access, but it is not requestable.)