All drugs change the way your body works and the way your mind works.

Your doctor might give you a drug to make your body work better, stop your body from producing too much of one chemical or tell your body to make more of another.

These drugs are called medicine. Your parents and doctor will tell you when it's okay to use these drugs, and how to use them properly.

If these drugs aren't used the way the doctor says, they can be harmful - and sometimes illegal. The same goes for medicine on the shelves at the pharmacy.

There are some drugs sold in stores that are harmful. These drugs come in cans, bottles and boxes and are only sold to grown-ups.

They include alcohol, such as beer and wine, and tobacco, such as cigarettes and chewing tobacco. Alcohol makes it hard to think, move and respond and it can hurt some of your organs. Tobacco can cause cancer whether it's chewed or smoked.

But some drugs are just plain bad for you.

They are so harmful, the United States government makes them illegal to use, have, sell or buy. They're often called illicit drugs or street drugs.

People use these drugs often to make their brain work differently so they feel different than they normally do, but street drugs can change the way your brain works permanently. That means, after using these drugs, your body will never go back to normal.