AIDS stands for Acquired Immune Deficiency Syndrome: Acquired means you can get infected with it, Immune Deficiency means a weakness in the bodys system that fights diseases. Syndrome means a group of health problems that make up a disease. AIDS is the final and most serious stage of HIV disease, which causes severe damage to the immune system. AIDS is a condition caused by a virus called HIV. This virus attacks the immune system of the body that fights off infections. When the immune system breaks down, person loses this protection and can develop many serious, often deadly diseases. These are called opportunistic infections (OIs) because they take advantage of the bodys week immune system.