the M and A button

hey i have abmw 325 is and i just got it and iwas wondering what does the M and A button mean i know the a is automatic and the M is manual but all you have to do is just press on the button also what is the best setup of even brake distribution can i get (im talking abotu the rotors whether or not i should put cross drilled on all 4 or slotted on all 4 or hlaf and half or just put normal brakes on it
paul baudier