This chapter provides a comprehensive introduction to the fundamental principles of polymer science, offering a foundational understanding for students. It begins with an overview of the historical background and evolution of polymer science, outlining the development of synthetic and natural polymers and highlighting key milestones in the field. The classification of polymers based on their origin, structure, and physical properties is also discussed. Furthermore, the chapter explores various polymerization techniques and polymer processing methods such as extrusion, injection molding, blow molding, and compression molding, explaining how raw polymer materials are transformed into functional products. Special attention is given to the influence of processing conditions on the final properties of polymer materials. Additionally, the chapter outlines the wide range of applications of polymers across various industries.