Autotrophic organisms refer to organisms that convert inorganic substances into organic substances through photosynthesis and the energy released by solar energy or chemical reactions. For example, green plants can synthesize organic matter through photosynthesis, and nitrifying bacteria can synthesize organic matter through chemical synthesis.

Heterotrophs refers to organisms that cannot synthesize inorganic substances into organic substances by themselves, including all kinds of animals, bacteria and other microorganisms.