Check out some of the following sites for more information on how to get started and create your own wiki! Some are free for K-12 educators.
According to Dictionary.com, a wiki is a web site developed collaboratively by a community of users, allowing any user to add and edit content.
A wiki's easy to use software allows you to create websites and so allow others to collaborate in building and editing them. Wikis may be one page or multiple pages. You can easily see the history of a wiki under the History tag and discussion is possible under the Discussion tag. Wikis may include a variety of embedded widgets (little program applications) including interactive maps, calendars, videos, slides shows, etc.
This video talks about what a wiki can do for you and your students!
Wikis in more user-friendly terms!