The full screen. It contains a header that looks like a pull-down projector screen, which will expand gracefully to contain whatever you want at the top of your page (Doesn't look quite as good in IE6, but great in other browsers). The left side is your posts, nicely formatted on a chalkboard. The right side is the WordPress "Sidebar" masked to look like every school's corkboard with pinned-up notes.
The header can contain a .gif image of your choice, the mortar board included by default for amusement. Your WordPress settings determine the wording.
The post looks like handwritten chalk to those viewers with any of several handwriting fonts installed. Users without them see a plain font. The hyperlinks on the board are lightened for contrast against the slate-colored blackboard.
Your WordPress Sidebar has never looked so good. Generated largely by the links, pages, and posts you make in WordPress, some notes look handwritten and some are formal. The fun pins and thumbtacks add a level of cartoony realism that you may find appropriate for your Blog.