What is the origin of the currently mined mineral-stone coal? How do people use it?

Underground coal seams were formed during the Paleolithic era. In those days, forests of large trees and ferns covered the earth’s surface. Plants died, fell to the ground, layered on top of each other. Under the influence of moisture and heat, dense condensates of wood were formed, which turned into coal. People use coal as a source of energy in production, for heating living quarters, for smelting metal ores.