In MediaWiki usage, users here means people who have IFWiki accounts and edit the wiki, as opposed to readers who only read the articles.
Users may create user pages about themselves if they wish, but this is completely optional. Note that user pages are distinct from articles in the People category. A user page is freeform, (mostly) unrestricted -- spam is still forbidden --, and expected to be primarily authored by the user himself or herself. By contrast, People pages are more formal and encyclopedic, subject to the People style guide, and may be edited by anyone (including the person being documented). Some users simply redirect their user page to their corresponding People page; that's okay too.
To date (December 2009), there are no cute badge-like templates created for user pages (e.g.: to declare one's affliation to a particular authoring system, language, country, birth month, etc.) as on Wikipedia. There has been no call for anything like that so far.
In 2009, IFWiki bureaucrats gained the ability to delete user accounts. Several accounts believed to belong to spammers were deleted at that time.
In October 2011, a new group of users called IFWiki:TrustedUsers was created so they could not be annoyed by captchas when editing articles, etc.
See also: Special:ListUsers