Coal is a fossil fuel that is used to generate electricity and heat. It is formed from the remains of plants that lived millions of years ago. The three solutions for the term COAL SOURCE are PIT, MINE, and STRIPMINE. A PIT is a hole or excavation in the ground from which coal is extracted. A MINE is a deep excavation in the earth from which coal is mined. A STRIPMINE is a surface mining technique where layers of soil and rock are removed to access coal reserves.