The thing that makes this a "Wiki" as opposed to just a collection of editable pages is the ability to create "links" between pages. In the "classic" formatting, a link is identified by creating a "WikiWord"; placing two or more initial-capitalised words together, CamelCase-style (e.g. HomePage). If the page exists, you'll see a link to it, if it doesn't exist yet, you'll see the name in red, which you can then click to create the page.
In addition, punctuation is not allowed in WikiWords—it appears automatically after edits have been saved. Click "WikiWord" under the "More" menu on the top bar to request punctuation and nonstandard characters for a title, and open the "How This Works" folder in the popup that appears for instructions. See also Text Formatting Rules for specific details about the format.