The basic structure of an antibody consists of two light chains and two heavy chains. The heavy chains are indistinguishable from each other and form the Y-shaped compact structure along with two similar light chains. The constant region and variable region of light chains differ, and the heavy chains vary for each subtype of an antibody. Antibodies are composed of 82-96% protein and 4-18% carbohydrate. The specific effector functions of antibodies vary based on their heavy chain structure. In summary, antibodies are essential components of the immune system that provide protection against foreign substances, and their classification and structure enable targeted responses to specific antigens.