A drug is a substance that alters the way in which your body works, it can affect your mind, body or both. In every society there are certain drugs which are used for medicine and other drugs used for fun.
Drugs are everywhere in society, people drink coffee and tea, some cigarettes and drink beer or wine. They think nothing of it, yet all of these things contain drugs - caffeine, alcohol and nicotine, all these drugs are legal.
Other drugs such as cocaine, ecstasy and heroin are all illegal. Which drugs are legal and illegal all depend on which country you are in.
Drugs can cause great harm to your body, this even applies to medicinal drugs. However, if these drugs make us better, it's worth taking the risk.