Can someone tell me please where or what the M1 and M2 keys are ? I am a real noob

M1 = mouse 1 (normally left click unless you've re-mapped it in windows as a left handed mouse)
M2 = mouse 2 (normally right click)

The M stands for mouse. M1 is your left mouse button and M2 is your right one. Unless you have a left-handed mouse of course in which case it'll probably be the other way around.