This document discusses the structure, types, classification, and properties of antibodies. It defines antibodies as proteins produced by the immune system that bind specifically to antigens. There are five main types of antibodies in humans - IgG, IgA, IgM, IgE, and IgD - which define the antibody's role in the body. Antibodies have a specific structure and classification that allow them to be indispensable immune system assets. They are also widely used in medical treatment strategies and therapies.