Utilitarianism is the term for a philosophy that places an absolute concept of Utility, (relatively to some notion of Good), as ultimately the only direct or indirect moral end. Though we could trace down the origins of Utilitarianism to Epicurus, the classical form of Utilitarianism is that defended by Jeremy Bentham and James Mill.

John Stuart Mill reformulated Utilitarianism to conciliate it with Liberalism, that teaches us how an absolute concept like Utility can only be partially and often erringly known. He thus made of Utilitarianism a frame for ethical reasoning rather than a set of dogmatic moral precepts.

In modern, simpler terms, we would remove the impertinent concepts of unknown absolutes, and replace them by variables, thus separating a frame for moral study, utilitarianism proper, from the choice of actual complete or incomplete systems of moral criteria.

Therefore, utilitarianism restated just says that in any consistent moral system, there is a principle of Utility that links any chosen notion of static Goodness (that evaluates Goodness of states) to a notion of dynamic Goodness (that evaluates Goodness of deeds), and conversely.

As for actual moral criteria, J.S. Mill discusses some, but you can find lots of them (consistent or not) in many different antique or modern works, and much more simply around you in everyday life. Cybernetics offer an interesting frame for proposing such moral criteria.