Turbines are rotary engines that extract energy from a fluid and convert it into electricity or utilize the rotation of the turbine to drive some useful function. This is accomplished by having a fluid flow across blades, so that the blades generate a force that imparts rotation to the rotor.

The most common turbines in industrial applications are steam or gas turbines. A steam turbine takes pressurized steam and runs it through blades that are attached to a shaft or drum and turn steam energy into rotation of the rotor. The turbine can utilize the rotation to create electricity or perform a useful function. A gas turbine combusts a fuel and uses the expanding combustion gas to flow through and spin the rotor.

The steam turbine has almost completely replaced the reciprocating piston steam engine because of its greater efficiency. About 80% of all electricity generation in the world is by use of steam turbines.