Board Thread:Support Requests - Getting Started/@comment-4482574-20140407181333/@comment-1330470-20140407191704

Wiki markup is the source code that produces a human readable page. Simple examples: for bold text one might type. For italics, one might type. If you edit a page using the Visual Editor, you're actually using that as an interface to edit the source code of the page (even though you might not actually see the source at any point). More experienced editors generally tend to prefer source mode, because it's more powerful than visual mode.

More advanced wikitext can be used to make tables, infoboxes, and more. You might check Nathan's link for a bit more info.