PrEP is one of the newest and most effective tools in the fight against the HIV epidemic. It's a medication that can be very effective in preventing HIV transmission if taken consistently. PrEP doesn’t prevent other sexually-transmitted diseases.
Right now the only pill approved to prevent HIV is called Truvada, which is taken by mouth every day. Truvada is currently only approved for use by HIV-negative people as PrEP in a few countries, but it is coming soon to many more.
Check out this ninety second video from Greater Than AIDS for more.