What kinds of traditional energy sources are there?

There are four kinds of traditional energy sources:

1. Coal is a solid combustible mineral gradually formed by complex biochemical and physicochemical changes of ancient plants buried underground;

2. Oil, one of the main targets of geological exploration, is a viscous dark brown liquid, which is called "industrial blood";

3. Water energy is a kind of energy, clean energy and green energy, which refers to the kinetic energy, potential energy, pressure energy and other energy sources of water bodies;

4. Wood is a lignified tissue, which is formed by plants that can grow twice, such as trees and shrubs.