Moral codes are often complex statements of right and wrong. Although some people might think that the moral code is simple, rarely is anything simple about one's morals or ethics or for that matter judgment of other morals. The difficulty lies in the fact that morales are often part of a religion and more often then not about culture codes.
A common version of a moral code is a legal code which states the penalties or corrective actions associated with any particular act (note that many of the legal codes are built on a foundaton of religion).
In some cultures, the relationship between moral and legal codes are often absolute - they're one and the same. Moral codes help drive personal conduct.
A related and more advanced (some say more corrupt) concept is an ethical code, which establishes tradeoffs and rationale for making decisions for the great good. Some of these resemble a moral code, most are less strict and make no special claim to actually distinguish 'right' from 'wrong' in any absolute sense. The ethical code is concerned with weighing all the negative and positive results of an action, and making a decision based upon the great good for a greater number.
Another related concept is the moral core which is assumed to be innate in each individual, to those who accept that differences between individuals are more important than Creators or their rules. This in some religious systems, (e.g. Taoism and Gnosticism) is assumed to be the basis of all aesthetics and thus moral choice. Moral codes as such are therefore seen as coercive — part of human politics.
See also: applied ethics.