An antibody is a special protein produced by the immune system to help fight off infections. When harmful invaders like bacteria or viruses enter the body, antibodies recognize and bind to them, marking them for destruction. This process is crucial for keeping us healthy and preventing illnesses. Antibodies are also used in medical treatments and tests. For example, vaccines train the immune system to produce antibodies against specific diseases, like COVID-19. Additionally, doctors can use antibody tests to determine if someone has been exposed to a particular infection, helping to manage public health effectively.