1) Good drugs: These have been given to you by a doctor to make you better whatever the case may be. Examples are penicillin.
2) Bad drugs: There are many examples of these. Heroin, crack, cocaine, speed, etc. Once you try these, your hooked (or should that be 'fucked'?). There are many diffrent reasons why people take these drugs but the important thing to remember is, they'll ruin your life.
Let us not forget that alcohol and caffeine are drugs too.
Two examples of drugs:
1) Doctor: Take two of these everyday and you'll feel right as rain in about two weeks.
2) Person X decided to try coke. He got addicted to it and fucked up his life.