Snow blowers scrape snow and, in some cases ice, from the ground using an auger, revolving on a horizontal axis.
The auger breaks up the fallen snow and the auger's forward rotation pushes the broken snow backwards into the body of the blower. It is then forced up and out of the exit chute. The smashed snow is then thrown from the chute in a stream.
(See image below).
In a single-stage blower the snow is forced up the chute directly by the action of the auger (See image below)
A Single Stage Petrol Snow Blower in Action
In a dual-stage blower the snow is pushed back to a secondary implement, a impeller, a kind of metal fan which further breaks up the snow and forces it up and out of the chute at a greater speed. (See image below).
A Dual-Stage Petrol Snow Blower in Action
The snow distribution chute will usually be rotatable and the 'pitch' (elevation) of the snow will usually be adjustable to throw the snow exactly where you want it.