MediaWiki is an open source Wiki engine licensed under the GNU General Public License.
On these help pages, you will find both a guide for using MediaWiki.
Navigating
Tracking changes
Accounts
Editing overview
Starting a new page
Images and other uploaded files
Special characters
Formatting
Referencing
Organizing
Saving effort (not having to write something, or copy and paste)
HTML in wikitext
Fixing mistakes and vandalism
Communicating
Testing