AIDS refers to Acquired Immunodeficiency Syndrome, a chronic and often life-threatening condition caused by the Human Immunodeficiency Virus (HIV). This condition is characterized by the progressive weakening of the immune system, making the body more susceptible to opportunistic infections and certain cancers.

AIDS is typically classified as the final stage of HIV infection. While not everyone with HIV will develop AIDS, the risk increases as the disease progresses without treatment. The diagnosis of AIDS is made when an individual with HIV experiences certain severe illnesses, specific opportunistic infections, or when their CD4 T-cell count falls below a critical level (typically 200 cells/mm³).

The symptoms of AIDS can include rapid weight loss, persistent fever, extreme fatigue, and prolonged swelling of the lymph nodes, among others. Treatment for HIV, primarily through antiretroviral therapy (ART), can effectively manage the virus and prevent the progression to AIDS, allowing individuals to lead healthier lives.

In summary, AIDS is a serious condition resulting from untreated HIV infection, marked by a greatly compromised immune system, which signifies the need for immediate medical intervention and lifelong management.