Acquired Immunodeficiency Syndrome, or AIDS, is a serious condition caused by the Human Immunodeficiency Virus (HIV). This virus attacks the body's immune system, specifically the CD4 cells, which help fight infections. Over time, if untreated, HIV can lead to AIDS, making it difficult for the body to defend itself against diseases and infections. People with AIDS may experience a range of symptoms, including weight loss, fever, and fatigue. The condition is diagnosed through specific tests that detect HIV and the level of immune system damage. While there is no cure, treatments are available to manage the virus and improve quality of life.