As I learns the ins and outs of my new Zoom B3 system, I've been doing a lot of research on each effect and what it actually does to my sound when I apply it to the bass. I had done some work on this topic back when I used to play around with digital recording, but since times change, I thought I'd revisit the topic.
Sweetwater.com has a great article on the subject of Pedals/Stompboxes and what each one does to your music.
They have info on every kind of effect you would need, including how multi-effect pedals work.
Pretty much self explanatory, distortion pedals make your guitar sound, well, distorted. Generally, this has come to mean everything from smooth tube overdrive to all manner of nasty, dirty, "my amp is exploding" tones and "scooped mids" pedals for death metal madness. The earliest example of distortion used in popular music was the three-note riff that was heard all over the airwaves when the Rolling Stones recorded "Satisfaction" (which, incidentally, was voted the number one rock song of all time by MTV). Jimi Hendrix loved running several pedals in sequence, like a fuzz, a wah and a "Uni-Vibe" (which we'll discuss in a bit). In fact, over 30 years after his tragic death, Jimi was still voted the world's greatest guitar player! Can you imagine having that kind of impact after a brief four-year career?
Check out the ENTIRE ARTICLE on Sweetwater's website.