When Utilitarianism was proposed, Mill/Bentham identified it as basically "pleasure good / pain bad". Since then, Utilitarianism has pretty much become a family of theories, largely differentiated by their conceptions of the good.

One common factor of ethical theories called "Utilitarianism" is that they tend to be agent-neutral; thus, one would not talk about "an agent's utility function", but "overall net utility" (a dubious concept).

"Consequentialism" only slightly more generally refers to a family of ethical theories that consider the consequences of actions to be the only consideration for morality.