Coal.

Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons.
Carbonization --> The chemical and organic process these dead organisms undergo to become coal 
Anthracite --> Coal is ranked very high if it has undergone a longer carbonization period.
Peat --> Coal that has not undergone too much carbonization is ranked low.

How is coal converted into electricity?

1. Coal is milled to a fine powder, allowing it to burn more quickly.

2. The hot gases and heat energy produced converts water in tubes lining the boiler into steam.

3. The high-pressure steam is passed into a turbine containing thousands of propeller-like blades.

4. The shaft rotation engages the wire coils and magnets in a generator connected to it.

5. Electricity is sent to the switchboard (transformer) where it is regulated and sent via on-land cables to homes.

Using coal to produce energy causes many some problems, usually on a greater scale than the use of oil or gas. 

Several forms of coal exist in the world.