l have a 94 bmw 525 and ive noticed that theres a botton right next to the shift gear thats labeled with the letter A on top and letter M on the bottom. What is it for???

That button is for two things
You slide it up & that just puts it into regular automatic mode this is what mode its in every time u start the car

The M stands for manual mode. When u slide it down to M basically all it does is lock it into what ever gear u put it into. So start up the car put it in M & just shift to what ever gear u want. And the car will start out in that gear. While driving if u want to go to 3 2 or 1 u just select that gear & the transmission shifts to that gear. Its just another ''steptronic'' manual shift system. Later car makers changed it to a ''cool'' name & changed the shifters to have a push up push down ability to shift the gears manually. Car makers did this because people simply could not handle using manual mode with the regular shifter, they were putting it in R & N by accident.

Note the manual mode only works with R N 3 2 & 1 There is no 4th or overdrive ability. Unless u get to 125-130 then the computer takes away ur control & goes into 4th & 155-160 it goes to OD or 5th..