the foot pedal

what can be done with it what ones and all the rest?

You can move your foot up and down and then the pedal, due to friction, moves up and down with you foot.

It tells you in your manual the real answer. Something like stop start, basic MMC if you ever read up about that.

You can trigger pads among other things.

... you can bind it to the f1 to f6 buttons and then use the functions assigned to them in the various screens ... like mute/solo, etc...
very handy for starting a direct recording, so you have both hands to play an instrument for example...

simple footswitches are the right ones, polarity doesn´t matter, the mpc senses the right setting automatically...

it is covered in detail in the manual - if you not have your mpc yet, just download it from the akaipro website...

peace jo