What's a guitar overdrive?

That wahwahwah sound is made when guitar players use a wah- wah pedal. You pump it back and forth with your foot to control 'treble'. Lots of treble, you get an 'ahhh' sound, but no treble, you get an 'oooo' sound. An overdrive is a box you plug into to increase the signal from your guitar to your amplifier that beefs up whatever you play so you can play power chord type metal, or screaming solos (like me)