Re: What's the difference in a Vibe pedal and a Tremolo pedal?
I hate the term 'Vibe'. That could be either of two effects, Vibrato or Uni-Vibe. A Vibrato modulates pitch as the other posters pointed out, and a Uni-Vibe is a phase shifter that is supposed to emulate a rotating speaker. True pitch vibratos are kind of rare, but you can hear Uni-Vibe everywhere from Jimi's Machine Gun, Robin Trower's Too Rolling Stoned, Pink Floyd's Breathe to Pearl Jam' Alive solo.
Also note that Leo Fender's naming convention is the opposite of the 'standard'. His volume effect on amps is named Vibrato when it's truly a Tremolo and his pitch changing bridge is called a tremolo when it's really a vibrato bar.