AIDS is the final stage of HIV infection. A person who is said to have AIDS when the person infected with HIV has two or more infectious diseases like tuberculosis, pneumonia. This means the person will have very low level of CD4 cells, so vulnerable to infections and infectious diseases. AIDS research includes drug development, vaccination, pre exposure prophylaxis and post exposure prophylaxis. From the past 20 years many researches are going on AIDS, still there is no cure for it.