Antibodies are specialized proteins produced by the immune system to identify and neutralize foreign substances, such as bacteria, viruses, and toxins. They are created by a type of white blood cell called B cells and play a crucial role in the body's defense against infections. Each antibody is unique and designed to target a specific antigen, which is a molecule found on the surface of pathogens. When an antibody binds to its corresponding antigen, it can neutralize the pathogen directly or mark it for destruction by other immune cells. This process helps the body remember past infections, allowing for a quicker response if the same pathogen invades again, a principle that underlies the effectiveness of vaccines.