I worked as licensed body and engine maintenance and ground crew, and gone on maintenance and transfer flights. Basically autorotation is like on planes, when engines crap out you glide and aim to do an emergency landing, since the rotor isn't a big fan, it's a rotating wing. While descending, the rotor spins and allows the gliding while slowing down the fall, like maple seeds; when near the ground the pilot can use the residual rotation energy to make a soft landing, like you said.