Biodegradable plastic refers to the product after microbial decomposition, and finally into water and carbon dioxide (completely disappeared), compostable, can be called biodegradable plastics. Common materials are PLA, PBAT, starch, etc. the products absolutely do not contain PE (polyethylene), PP (polypropylene) and other non degradable plastic components.
Note: the so-called photodegradation and ordinary plastics with additives are only disintegrated into small particles, which is more harmful. There are also starch based plastics, which are only partially degraded when filled with starch in ordinary plastics. Plastics themselves do not degrade.