What does the do not disturb setting do? (iPhone 4)?

In the settings there's a switch for do not disturb. What's that for?

The phone doesn't alert you if you get a new call or text or notification which is good when you are sleeping or in a meeting.

I use that setting at night so I don't wake up to texts/calls because I have to leave my sound on at night so I can wake up to an alarm. But Basically it makes it so your phone won't light up or vibrate at all, so you can get through a meeting or go to bed without being disturbed by texts/calls/notifications/etc. But all of those notifications will appear when you "wake" your phone. I love that apple made this feature! Definitely recommend it while you're sleeping or at school.