If PrEP is like birth control, then PEP is like emergency contraception.
PEP (Post-exposure Prophylaxis) is a medication regimen someone who is currently HIV-negative can take to reduce their risk of becoming infected after they have been exposed to HIV. PEP must be started within 72 hours after a possible exposure and continued for 28 days. If you feel you may need PEP, please visit your local emergency room or urgent care.
Post = after
Exposure = coming into contact with HIV
Prophylaxis = treatment to prevent an infection from happening