It is the protection provided by the immune system to ward off any kind of infections, disease or other biological invasions. It is made up of both specific and non-specific components. Non-specific barriers are essentially those cells that act as barriers for noth pathogenic and non-pathogenic foriegn objects and are not for any specific pathogen. There are other cells that align change themselves to kill certain types of pathogens as well. There are mainly two types of immunity innate immunity and aquired immunity. Innate immunity is that kind that a person is born with. Aquired immunity is that kind which is a reaction of the body to previouly encountered pathogens — in cases where a person suffers from conditions like chicken pox, the body prepares antibodies to protect itself form any further infection by the same pathogen.