All three contain antiretroviral medicines in different combination for different purposes:
PrEP is a pill that has 2 anti-HIV medicines taken daily to prevent HIV for HIV-negative people. PrEP is taken before you think you might be exposed to HIV.
PEP is taken within 72 hours after exposure to HIV (e.g. after rape) for 28 days to prevent HIV. PeP is taken after you think you have been exposed to HIV.
ART is a 3-medicine treatment for HIV-positive people that reduces the levels of HIV in a person’s body. ART helps the body stay strong and helps it fight off infections and other illnesses.