First of all HIV stands for the Human Immunodeficiency Virus and AIDS stands for Acquired Immune Deficiency Syndrome. HIV = AIDS, basically HIV turns into AIDS once it gets more serious.
You can get it by having sexual intercourse with a person with HIV. That’s why you always need to have protected sex. HIV is a virus that attacks the cells of the immune system. The virus is very “silent”; it might not show any signs for years. Over time the virus reduces the strength of the immune system and leaves the immune system vulnerable for other diseases. HIV can be transmitted by blood, semen, vaginal secretions, and breast milk.
HIV can not be transmitted by hugging, shaking hands, sharing foods or drinks, or a kiss.

So if you get HIV, you have to go get treated immediately before it turns into AIDS.

Currently there is no cure for HIV or AIDS, so the best you can do to HIV/AIDS it prevent it. For example, use condoms, etc.