HIV is the virus that causes the disease, AIDS. The only way to get HIV is if you get certain body fluids of a person with HIV into your own body.
These fluids include:
- Vaginal Fluids
- Breast milk (from a mother to a baby)
Kissing on the other hand is usually considered safe as saliva does not pass HIV.
However, as About's Guide to AIDS explains:
Open-mouth kissing is considered a very low-risk activity for the transmission of HIV. However, prolonged open-mouth kissing could damage the mouth or lips and allow HIV to pass from an infected person to a partner and then enter the body through cuts or sores in the mouth.
Even so, this would be incrediably rare and kissing is not usually considered a risky activity.