Here's a short snip from the tutorial:
Compared with a traditional Pocket PC, the Smartphone OS may seem simplified, however, (among other things) a major difference is found in the way customization occurs. Specifically, Homescreen (today page) layout, appearance, and function. Historically, PPC users would install tsk files and then add/remove plugins via the settings menu. Smartphone's handle this area quite differently. If the whole Homescreen thing is a bit of a mystery, or you are simply bored with your current layout, read on. Today we're going to take a closer look at the Homescreen concept and hopefully answer a few of those queries you may have.