Antibodies are important proteins produced by the immune system which recognize and bind to specific antigens, providing immunity against infections caused by viruses, bacteria, and parasites. There are five classes of antibodies with varied functions and structures. The most common antibody is IgG, found in the bloodstream, and IgM is the first produced during an infection. IgA provides immunity for mucous membranes, IgE is essential for allergies and parasite defense, and IgD has an unknown function. Antibodies are crucial for good health and are used in vaccines and treatments for various diseases.