HIV (Human Immunodeficiency Virus) is a virus that causes AIDS (Acquired Immunodeficiency Syndrome), a health condition in which a person is affected by a series of diseases because of poor immunity. HIV by itself is not an illness and does not instantly lead to AIDS. An HIV-infected person can lead a healthy life for several years before he/she develops AIDS.

As the name, Acquired Immunodeficiency Syndrome, indicates, AIDS is a health condition that results from the deficiency in the body's immunity following HIV infection. HIV attacks the human body by breaking down its immune system that is meant to fight diseases. Over a period of time, the immune system weakens and the body loses its natural ability to fight diseases. At this stage, various diseases affect the infected person.