#1
a question of curiosity: what is it that pedals actually do to affect your tone? how does it differ for different effects? and whats the difference between the pedals with say one or two effects on them (ie: a BOSS overdrive) and the pedals with hundreds of different effects (ie:a digitech RP-200). thanks in advance
#2
It depends on the pedal. Distortion pedals clip the sound wave, compressors modify the attack and release of the note, many effects modulate the incoming signal, etc.

Single effect pedals are generally much better units than multieffects, especially if the single effects are analog.

These are all generalizations, pedals vary a lot.
#3
whell how does it affect tone? that depends on the pedal.
Lets start with basic distortion. In a nutshell this si what it does.
Do you know what a Sine Wave is?

Yes, imagine that is what a clean guitar tone looks like under an osiliscope (the thingy electricans use to see these things. The sound of a clean guitar doesn't look anythign liek this, but for graphic representation, work with me here!)

This is what that same guitar sound looks like after distortion.


And for your quesion about multi-effects and single effects, single effects are made with an advanced array of transistors, resistors, and capacaters. Like they used to do way back in the 50s and 60s before the modern transistor.
Digital effects are made liek computers, with computer chips and stuff.