Well to put it in simple terms emaan, the M drive is a button which helps the driver select the mode of driving - dynamic or normal to sport to sport plus. The settings (caution technical stuff = DME system, DSC, EDC, Servotronic steering and the M DCT Drivelogic) can be preset and at the point of driving all the driver has to do is press the button of his or her suitable choice. You can read material online about the technicalities behind these settings.