From The Catholic Encyclopedia at New Advent:
It is necessary at the outset of this article to distinguish between morality and ethics, terms not seldom employed synonymously. Morality is antecedent to ethics: it denotes those concrete activities of which ethics is the science. It may be defined as human conduct in so far as it is freely subordinated to the ideal of what is right and fitting.
A distinction must be made between ethics and morals, or morality. Every people, even the most uncivilized and uncultured, has its own morality or sum of prescriptions which govern its moral conduct. Nature had so provided that each man establishes for himself a code of moral concepts and principles which are applicable to the details of practical life, without the necessity of awaiting the conclusions of science. Ethics is the scientific or philosophical treatment of morality. The subject-matter proper of ethics is the deliberate, free actions of man; for these alone are in our power, and concerning these alone can rules be prescribed, not concerning those actions which are performed without deliberation, or through ignorace or coercion. Besides this, the scope of ethics includes whatever has reference to free human acts, whether as principle or cause of action (law, conscience, virtue), or as effect or circumstance of action (merit, punishment, etc.). The particular aspect (formal object) under which ethics considers free acts is that of their moral goodness or the rectitude of order involved in them as human acts. A man may be a good artist or orator and at the same time a morally bad man, or, conversely, a morally good man and a poor artist or technician. Ethics has merely to do with the order which relates to man as man, and which makes of him a good man.