On MediaWiki sites such as WikiIndex, and virtually all of the Wikimedia Foundation's 900 wiki, a detailed list of all group rights can be found at Special:ListGroupRights. Individual wiki users are assigned to one or more specific user groups, either automatically by system default, or by manual 'promotion'; and can be given greater or lesser permissions based on their edit history, conduct, collaboration, enthusiasm, etc, and also by personal request. Certain specific user groups include allowing the permission to grant other users permissions.
All MediaWiki site installations are provided with a standard or default range of user groups – typically 'all', 'users', 'autoconfirmed', 'administrator', and 'bureaucrat' – the latter of which is usually the most senior, with the greatest overall range of permissions and privileges. These standard user groups may be supplemented by the addition of further established conventional user groups by the wishes and needs of the site owner(s). There is also the scope to add new additional customised user groups, and also ability to totally rename all existing user group names into something more frivolous, fanciful, or even humourous; as is typical on many of the parody sites.
It should be noted that the now-common range of user groups were not available on the original wiki engine: WikiWikiWeb (also known as 'Ward's Wiki'), nor any of the very early development wiki engines from that original.