Machine

There are five primary varieties of gasoline engines, all operate differently and some take multiple fuels.

1.  Otto stroke (the most common in use today).  This four-stroke engine delivers power cleanly but is heavy and complex.

2.  Kleinman stroke (used in lightweight and short-life applications).  This two-stroke engine uses ports along the side of the cylinder to charge the cylinder with fuel and exhaust the burned gasses. 

3.  Wankel rotary (used in some sports cars, light trucks, and motorcycles).  This engine uses a triangular rotor inside an oval cylinder.  It is somewhat more efficient than Otto stroke engines and is more robust, but manufacturing cost is much higher. 

4.  Gasoline fired turbine (used where power to weight is the determining factor).  This engine is used on helicopters and some propeller driven aircraft.  It can be converted to burn kerosene or diesel fuel.

5.  Gasoline fired steam (either turbine or piston variants). 

The internal workings and engineering criteria can be a little involved.