For large or largish generators steam turbines gas turbines wind turbines water turbines diesel engines
at power plants (electricty generating stations), they use steam pressure to turn large turbine blades. the shaft of the turbine is coupled (connected) to a generator. Around the neighborhood after a storm/power outage, private citizens use small gasoline powered engines to turn small generators. There are a zillion others to numerous to mention but I'll go until they stop popping into my brain--- diesel/ natural gas/ waste boiler heat, hydroelectric at a dam, the little thing on you bicycle that rubs along the wheel and turns on the lights, gilligan pedaling that bike .....
