Can someone tell me whats is a black cadillac pill and what is it for?

SLANG for: black cadillacs - Amphetamine

Amphetamine its pharmaciutical speed. It will keep you up for days and is unsafe to take without being monitored by a doctor when taking medication you put your own life at risk not your doctor. You can get the slang words for street drugs at this website http://www.noslang.com/drugs/dictionary/b

There is a pill identifier on this site.

But I suggest you call your local drug store and ask them, I am sure they will be able to provide you with the right answer, and it will take less of your time, sometimes finding pills online with limited information is difficult.

Take care and good luck... by the way there is a member, mrspage82, she is very good at finding pills and giving you all the information you need.