Well, sex is when two grown-ups who really like each other do a special thing together. They get very close to each other and do things that make them feel good. But it's important to remember that only grown-ups should do this, and they should always make sure they both want to do it and use protection to be safe from getting sick or having babies.
Drugs are things that can make you feel different or weird inside. Some grown-ups choose to take drugs to feel happy or relaxed, but it's not always safe. Some drugs can make you very sick or even hurt your body. That's why it's important to always say no to drugs and talk to a grown-up you trust if someone tries to offer you drugs.