HIV stands for human immunodeficiency virus. HIV is the virus medical researchers believe causes AIDS. (Medical researchers believe that HIV is causative agent of AIDS).HIV is different from most other viruses because it attacks and damages the immune system. The immune system gives our bodies the ability to resist against infections. HIV finds and destroys a type of white blood cell (T cells or CD4 cells) that the immune system must have to fight disease.
There are some medical treatments that can slow down the rate at which HIV weakens the immune system and that can prevent or cure some of the illnesses associated with advanced HIV disease. As with other diseases, early detection offers more options for treatment and preventive care.

Anonymous HIV and STD testing, for more details: HIV Reliable Testing