HIV, or Human Immunodeficiency Virus, is a retrovirus that attacks the immune system, specifically targeting CD4+ T cells, leading to progressive immunosuppression. Its clinical significance lies in the risk of opportunistic infections and the development of AIDS if untreated, highlighting the importance of early diagnosis and antiretroviral therapy. A key complication associated with HIV is the increased susceptibility to infections such as tuberculosis, which can be life-threatening.