Answer:
There are a many ways to produce electricity. Electrons can flow between certain different materials providing a current, as in a common battery. While reliable and portable, chemical batteries run down quickly. To provide the large amounts of steady power demanded by modern societies, large power plants have been built. Most power plants make electricity with a machine called a generator.
A 1925 Turbine Rotor
A 1925 turbine rotor for a Westinghouse generator, Image #21.035, Science Service Historical Image Collection, National Museum of American History
Generators have two important parts: the rotor (which rotates) and the stator (which remains stationary). Generators use the principle of electro-magnetic induction, which exploits the relation between magnetism and electricity. In large AC generators, an outer shell with powerful magnets rotates around a stationary "armature" which is wound with heavy wire. As they move, the magnets induce an electric current in the wire.
It is important to recognize that electricity is not mined or harvested, it must be manufactured. And since it's not easily stored in quantity, it must be manufactured at time of demand. Electricity is a form of energy, but not an energy source. Different generating plants harness different energy sources to make electric power. The two most common types are "Thermal Plants" and "Kinetic Plants".