HIV stands for Human Immunodeficiency Virus, which is a virus that attacks the immune system, specifically the CD4 cells (T cells) that help the body fight off infections. If left untreated, HIV can gradually weaken the immune system, making it harder for the body to defend against illnesses and infections. AIDS stands for Acquired Immunodeficiency Syndrome. It is the final stage of HIV infection, characterized by a severely weakened immune system. People with AIDS are more susceptible to various opportunistic infections and certain types of cancers that a healthy immune system would normally be able to fight off. In essence, HIV is the virus that can lead to AIDS if not properly managed with medical treatment. With advancements in medical care, many people with HIV can lead healthy lives and prevent the progression to AIDS.