Autotrophic organisms: organisms that can synthesize their own organic matter from inorganic substances belong to autotrophs. Such as cyanobacteria, nitrifying bacteria and green plants. Heterotrophs: Organisms that can only ingest ready-made organic matter from outside belong to heterotrophs. Such as most animals and fungi.

Conceptually, autotrophs refer to organisms that can synthesize organic matter from external inorganic substances, such as green plants and nitrifying bacteria. Heterotrophs is an organism, such as human, which can't synthesize organic matter from external inorganic substances by itself, but can only get energy by eating. Therefore, the fundamental difference between autotrophs and heterotrophs lies in whether they can synthesize organic matter from inorganic substances.