Whammy Bars

There's a stick on guitars, they make noises called dive bombs and the like. I've heard it be called a Whammy, Vibrato, or Tremolo Bar. The video I checked out earlier was kinda useless explaining how it works, but this guy I have a college class with [I'm starting to find a guitarist in every class] said it was just like vibrato [where you wiggle a string with your finger] but it does it to all the strings at once.

It works by shaking the bridge, which explains why several people reported some guitars going out of tune when they used the Whammy Bar alot.