Polymer materials are long chain molecules made of repeating monomer units. They include plastics, rubbers, and fibers. Polymers are classified as thermoplastics, thermosets, homopolymers, copolymers, and natural polymers. The structure and properties of polymers depend on factors like chain length, branching, and cross-linking. Polymers have a variety of applications including packaging, insulation, automotive and medical parts due to their low cost, low density, and moldability.