The document discusses biomaterials, which are materials used in medical applications that interact with biological systems. It defines biomaterials and outlines their classification as natural or synthetic. Natural biomaterials discussed include proteins, cellulose, chitin, and polynucleotides. Synthetic biomaterials include polymers like PMMA, ceramics like calcium phosphate, and metals like titanium. Common applications of biomaterials are described like implants, prosthetics, and medical devices used in the skeletal, cardiovascular, and sensory systems.