HIV (Human Immunodeficiency Virus) is a virus that attacks the body’s immune system, specifically targeting CD4 cells, which play a crucial role in fighting off infections. Over time, HIV can weaken the immune system, making it harder for the body to fight infections and diseases. If left untreated, HIV can progress to AIDS (Acquired Immunodeficiency Syndrome), a more advanced stage of the disease where the immune system is severely compromised.