Consequentialism is the class of normative ethical theories holding that the consequences of one's conduct are the ultimate basis for any judgment about the rightness of that conduct. Thus, from a consequentialist standpoint, a morally right act (or omission) is one that will produce a good outcome, or consequence.
Consequentialism is usually distinguished from deontological ethics (or deontology), in that deontology derives the rightness or wrongness of one's conduct from the character of the behaviour itself rather than the outcomes of the conduct. It is also distinguished from virtue ethics, which focuses on the character of the agent rather than on the nature or consequences of the act (or omission) itself, and pragmatic ethics which treats morality like science: advancing socially over the course of many lifetimes, such that any moral criterion is subject to revision. Consequentialist theories differ in how they define moral goods.
Some argue that consequentialist and deontological theories are not necessarily mutually exclusive. For example, T.M. Scanlon advances the idea that human rights, which are commonly considered a "deontological" concept, can only be justified with reference to the consequences of having those rights. Similarly, Robert Nozick argues for a theory that is mostly consequentialist, but incorporates inviolable "side-constraints" which restrict the sort of actions agents are permitted to do.