A wiki is a slightly unusual concept for people used to traditional newspapers, magazines and websites. Unlike a traditional website where the pages are created and edited by one person, or a team working under the direction of one person, on a wiki any member can change a page. So for, example if there's something on this page or in this sentence you think can be improved, please make the change.
It's important of course to try to make things better rather than worse. And to be sensitive that the earlier writer may have been trying to communicate something you don't yet quite understand. But the whole idea of a wiki is that the interplay between authors creates something better than just one author working alone.
According to Wikipedia, the world largest wiki site:
A Wiki ([ˈwiː.kiː] <wee-kee> or [ˈwɪ.kiː] <wick-ey>) is a type of website that allows users to add, remove, or otherwise edit and change most content very quickly and easily.
This wiki is built using wikidot software from the Wikidot.com network.