This is a private area (unless you say otherwise) for you to preview your writeups before submitting them. The HTML and text is displayed just like a regular writeup, except privately, viewable only by you and yours. You can choose to have other people be able to view it, so that you can get comments on a writeup or what not, but this is not the default. Use it to test or preview HTML (all the tags work just the same), or just to keep random notes to yourself.