The document discusses HIV and AIDS. It defines HIV as the human immunodeficiency virus that attacks the immune system. AIDS is defined as acquired immunodeficiency syndrome, which is the medical condition where the immune system is too weak to fight infections. HIV damages CD4 cells, which are part of the immune system. This ultimately leads to immunodeficiency and multiple opportunistic infections, which characterizes AIDS. The stages of HIV infection are also outlined, from initial infection to symptomatic stage to AIDS. Treatment with antiretroviral medicines can stop progression to AIDS.