In a wiki, every time someone edits a page a new version is created. The history feature is then used to view any of the olders versions of a page. It ensures that the work of all editors is viewable and recoverable, even if that work is no longer on the current version of the page.

Any version can be compared side-by-side with the most current version, or the next version.

Each difference can be highlighted.

You can also see a list of all changes accross the system using the Recent Changes link on the HomePage under Quick Links.