Page Permissions

If a wiki supports 'page permissions', it means you can control access in some way, on a per-page basis.

Details vary from one implementation to another, but typically it might mean that you can set a page as 'locked' (a.k.a. 'protected'), so that people cannot freely edit that page. With basic permission system, there is one administrator password. More advanced systems might have permission levels relating to different users/groups/roles. Access Control List (ACL (Access Control Lists)) style permissioning systems take this idea further

Note that one of the great things about wiki software is its “Soft Security” approach. If you are tempted to go locking down and restricting editing of your wiki, perhaps you need to think again. Would it really do any harm to allow everyone to edit this page? Websites like wikipedia have demonstrated that open editing is a great thing, since everyone can revert bad edits too. This is a fundamental part of the wiki philosophy.

Having said that… A popular use of this feature, is to block editing on your main page, since this is particularly vulnerable to regular vandalism. Certainly there's no harm in having such features at your disposal.