What is the difference between walk power and self propell lawn mowers?

Self propelled lawn mowers have gears or chain links attached on the axles that mesh with drive gears mounted on a shaft connected to the engine crankshaft. They move by themselves at a steady speed. The rate of speed on some models can be set by the operator at slow, medium or fast depending

on how fast the operator wants to walk and guide the mower at the handle bars. On steep climbs they are easier on the operator because with a normal walk behind the operator has to push and guide the lawnmower from the handlebars.