Normal autorotation, lift vector is inclined slightly forward (relative to the blade) so it pulls the rotors round and has enough oomph to overcome the gearbox frictional losses, oil & hydraulic pumps, tail rotor drive etc. this all despite a significant positive pitch remaining on the blades with the lever fully down.
If the angle of attack (being dependant on the blade pitch angle, vertical speed and the forward speed ie rpm) exceeds the critical value, then the blade stalls. Now the lift vector is much smaller but also inclined well aft (relative to the blade), so as to drag the blades and make them slow rapidly. The increased rate of descent increases the angle of attack, as does the slowing. Unlike a FW you can't just pitch the nose down to recover because the blades are pointing in all directions.