This is a type of page where users, if they have the appropriate rights, will see an "edit" button. They can then modify the page and save it. The whole idea of a "wiki" is to allow collaborative creation of information. If you know something about a particular topic, you should add your knowledge to the wiki page. Wikipedia is one massive set of wiki pages where knowledge is created and shared by many, many people.
We use a specific web application called "Tiki Wiki" for this site. It has certain formatting capabilities that you can use on a wiki page, or even in a forum post. Here is a link to the formatting documentation.
You create the formatting by using a few special "codes" in your text. A few of the basic formatting tricks are:
!!!Heading Three (etc.)
''Italic'' (this is two consecutive single quotes ' not a double quote ")