What is the difference between PrEP and PEP?

PrEP stands for Pre (before) exposure prophylaxis.

PrEP is a daily preventive treatment taken to Prevent HIV.

PEP stands for Post (After) exposure prophylaxis.

PEP is a medication that is administered to HIV negative people that have been in a high-risk encounter (high-risk intercourse) within the last 72 hours.

To make it easier to understand, PrEP is like an oral contraceptive. PEP is the day after pill.