Immunity is the balanced state of having adequate biological defenses to fight against infections, diseases, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases. Innate immunity, or nonspecific immunity, is the natural resistances with which a person is born. It provides resistances through several physical, chemical and cellular approaches. Adaptive immunity is often sub-divided into two major types depending on how the immunity was introduced. 'Naturally acquired immunity' occurs through contact with a disease causing agent, when the contact was not deliberate, whereas 'artificially acquired immunity' develops only through deliberate actions such as vaccination.