what is a crybaby? wah wah whatever

i am buying a new guitar and amp and pedal. on musiciansfriend.com the guitar i want comes with a free crybaby pedal. iv never known what that pedal does. iv asked ppl but they dont know either. does it just make a wah wah sound when u push on the pedal? it has a button under the pedal. what does the button do? does it turn it on and off? if u push too hard does it turn it off?
i know im prolly the only person that doesnt know. so laugh it up. but please answer.

It's basically a tone knob (like what's on a guitar) that you can control with your foot. By rocking it back and forth, it's kind of like turning the tone knob on your guitar back and forth. The wah pedal offer's a lot more sweep than a tone knob though, but it's the same concept.

The button under the pedal turns it on and off.

Listen to Jimi Hendrix's Voodoo Child (or most of Hendrix for that matter), he uses it all over that song.