Plastics can be divided into two major types
Thermoset or thermosetting plastics. Once cooled and hardened, these plastics retain their shapes and cannot return to their original form. They are hard and durable.Examples include bakelite used to make switch boards
Thermoplastics. Less rigid than thermosets, thermoplastics can soften upon heating and return to their original form. They are easily molded and extruded into films, fibers and packaging. Examples include polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).
All plastics fall into these categories. There are other kind of classification based on the recycling nature of plastic which is a very broad one.