Immunity is a branch of biology that focuses on the body's ability to resist infection and disease. It encompasses the study of the immune system, which is a complex network of cells, tissues, and organs that work together to defend the body against foreign invaders such as bacteria, viruses, and parasites. The immune system functions by recognizing and destroying pathogens, as well as maintaining a memory of past infections to provide faster and stronger responses in the future. Research in immunity aims to understand how the immune system functions, how it is regulated, and how it can be modulated to improve health and treat diseases. This field is crucial for the development of vaccines, treatments for autoimmune disorders, and therapies for cancer.