This document discusses various types of plastics and polymers. It provides 13 reasons why plastics are commonly used, including being lightweight, low cost, and available in various colors and forms. It then covers polymerization processes and how monomers link together to form polymers. The rest of the document categorizes and classifies different types of polymers based on their structure, manufacturing method, processing type, crystallinity, and applications. Key polymer types discussed include polyethylene, polypropylene, polyvinyl chloride, polystyrene, nylons, and rubbers.