OK, it sounds simple, and it probably is if you're sitting at your desktop with Gnome or KDE fired up. However if you're looking on a server half way across the world, using the command line its not so easy.
There are a number of tools which are useful in finding out things about your filesystem. ls, du, df are three of them, but sometimes they just don't give you the information you need. In my case I'm backing up a server to a remote location. The script was timing out becase I was trying to back up too many files at once, so I needed to find the number of files in each subdirectory.