Manual:$wgGroupPermissions

Details
$wgGroupPermissions is a two-dimensional array indexed by user group and available permissions; for example, " " allows registered users to edit. These groups can be assigned to users through the wiki Special:Userrights interface.

For in-depth documentation, see Manual:User rights.

Default values
For the more info, visit (see Manual:User rights).

Note that this list is incomplete - so far it only goes as far as 1.7.0

Here are the default values. The comments after each item indicate the version of MediaWiki in which the setting was added.

Note that those with the 'deletedhistory' right can view deleted history entries, but not see or restore the text.

Use by extensions
Some extensions, such as RenameUser or MakeBot, add new rights which can be configured and assigned in the same manner.