The belief that what ultimately matters in evaluating actions or policies of action is the consequences that result.
Consequentialism is sometimes conflated with utilitarianism, which is a mistake, as utilitarianism is but one kind of consequentialism. Kinds of consequentialism--in a broad sense of 'consequentialism' that not all philosophers would countenance--can be distinguished by the subject who is supposed to enjoy the consequences. That is, one might ask "Consequences for whom?" Egoism can be understood as individualist consequentialism according to which the consequences for the agent herself is taken to matter most. Utilitarianism, on the other hand, can be understood as collectivist consequentialism according to which the consequences for some large group (humanity perhaps, or the sum of sentient beings) is of the greatest moment. These views, while both consequentialist, can be in stark contrast. Individualist consequentialism may license actions which are good for the agent, but are deleterious to general welfare. Collectivist consequentialism may license actions that are good for the collectivity but deadly for individuals. Some environmentalists seem to take the entire environment or ecosystem to be the relevant patient of consequences. The entire universe might be the subject, the best action being the one that brings the most value into the universe, whatever that value might be.
Another way to divide consequentialism is by the kind of consequences that are taken to matter most. The most popular form of consequentialism is hedonic consequentialism, according to which a good consequence is one that produces net pleasure, and the best consequence is one that produces more net pleasure than any of the alternatives. Closely related is eudaimonic consequentialism, according to which full, flourishing happiness (which may or may not be the same as enjoying a great deal of pleasure) is the aim. However, one might fix on some non-psychological good as the preferred consequence of actions. For instance, certain ideologues seem to be consequentialists with regard to material equality or political liberty, regarding gains in these things as desirable in themselves, regardless of other consequences. One might also adopt a beauty consequentialism, in which the ultimate aim is to produce beauty. Similarly, one might find nothing of greater gravity than the production of knowledge. One can also assemble packages of goods, all to be promoted equally. Since in this case there is no overarching consequence to aim for, conflicts between goods are to be adjudicated not by some ultimate consequentialist principle, but by the fine contextual discernment and intuition of the agent.
Consequentialism is often contrasted with deontologism. However, this may be mistaken. Many forms of consequentialism at bottom are deontological, demanding that we simply have a duty to produce a certain kind of consequence, whether or not that kind of consequence personally moves us. And even paradigmatic deontological theories, such as Kant's, at times seem consequentialistic. For instance, one might argue that for Kant, the more expression of rational nature, or the good will, the better. It is difficult to find a theory that posits an intrinsic good (such as the good will in Kant) in which it is not better to have more of the intrinsic good. A more fundamental distinction is between theories that demand that agents act for ends in which they have some personal interest and motivation (actually or counterfactually) and theories that demand that agents act for ends perhaps disconnected from their interests and drives. - WillWilkinson