The backup function provided by Apple is easy and fast. The backup function can backup most of the data, including settings, apps (with the data), music, photos. The app data is very very important. For example, if you have play all the levels of Plants vs Zombies, you don't need to start from beginning since the app data for the game is also restored.
Backup function is very useful when you plan to do some major changes to your iPad or iPhone, like restore to a new iOS or jailbreak.
There are two ways to backup: through iCloud and through iTune. I recommend iTune since it is much faster and there is no limit for the space (stored in your hard disk).
The steps for back up and restore can be found at:
Note that when restoring, the iPad/iPhone will restart and then start the restore process. It takes about 30 minutes to restore around 15G of data for my iPad.