Linked from
The 11 pages that link to Propeller, each with the reason it gives.
AirfoilRelated: Each propeller blade uses airfoil sections to create force as it rotates.
Aircraft engineRelated: It converts an engine's shaft power into thrust.
MultirotorRelated: Each powered propeller supplies one of the multirotor's lift-producing forces.
Model aircraftRelated: Propellers provide propulsion on many powered model aircraft.