often the opposite of mud... in mud, you want the tires spinning to clean themselves out and regrab.... in snow, spinning will cause the snow to pack, and create ice, you want to deliver just enough torque to move, any more will keep you still, or send you down....
you can't steer when you are on your brakes and sliding, so if you find yourself sliding, let off the brakes, steer, then try stopping again... if you are headed down a hill or into danger... i often find it best to let off the brakes, and head for the softest backstop near