HIV stands for Human Immunodeficiency Virus. It’s a virus that attacks and weakens the immune system. If it’s untreated, HIV causes so much damage that the body is no longer able to defend itself.
People who have been infected with HIV are often referred to as being HIV-positive (sometimes this is written as HIV+, or even +ve). Although there have been many advances in treatment in recent years, there is still no cure for HIV infection.