Turbines convert the kinetic energy of a moving fluid or gas into rotational energy that can be used to drive a dynamo and generate electricity. Usually, the source of the kinetic energy is steam, although it can sometimes be water.
In a typical turbine setup, fuel is consumed at one end of the system to generate heat. The fuel can be almost any energetic reaction. Coal, petroleum, nuclear decay and even the heat of underground geothermal activity are all used to heat water.
Water thus heated is then piped along the system to the turbine. Escaping its pipe at high temperature and under pressure, the water imparts considerable force to a turbine's impeller, which is a threaded surface that converts the pushing action of the steam into a twisting motion. The turning shaft spins a disc at the far end that passes magnets through coils of conductive wire. This oscillating magnetic field induces a current in the wires, which strengthens the magnetic field.
The magnetic field then induces a stronger current in the wires. When the current is near peak output, electricity can be sent down the wires to consumers, machines that use the energy right away or batteries that can store the electricity for later use.