Anyway, the point is, when you come to any wiki site, you might not know exactly where to start reading or how to get a feel for what's going on. By clicking RecentChanges, you can see what pages other people have been working on and when (as long as the changes were recent!) and you can directly click on the names of those pages to see what's been happening. If people have set their Preferences you'll also see their names next to the page they recently changed. Now is it clear?
RandomPage is also a cool feature to find pages that might not have changed recently (although they might have), and if you then find them interesting, you can change them, making them pages that have changed recently and thus showing up on RecentChanges for other RecentChangesJunkies? to notice.