PrEP (Pre-exposure Prophylaxis) is for people who are not living with HIV and would like to remain HIV-negative and is a combination of safe sex practices and a daily medication. Currently, the only FDA approved medication for PrEP is Truvada®. It was approved for HIV prevention in 2012 and contains two medications: tenofovir and emtricitabine.
Pre = before
Exposure = coming into contact with HIV
Prophylaxis = treatment to prevent an infection from happening
Think of it like this: Truvada® for PrEP is like birth control. You take a pill every day, and if you are exposed to HIV, there is a 99% chance that you stay negative for HIV! Just like women who take birth control pills every day and have sex without getting pregnant.