You wouldn't believe how many times I get asked this question. Personally, I don't care at all whether you call them ethics or morals, just as long as you have thought your code of behavior through, and act in a manner consistent with that thinking.
But for those of you who do care:
The dictionary defines morals as "principles of right and wrong conduct."
Ethics are defined as a "system of morally correct conduct."
So I suppose you could say that morals are the principles you live by, and ethics are the system by which you put those principles into action.