Utility has two primary meanings:
Utility is an economic term representing someone's satisfaction or happiness. The utility of a good, for example, is the satisfaction it brings to a consumer.
Utility functions are mathematical ways of representing the benefits accruing to a consumer from his consumption of various goods. A utility function, in conjunction with a budget constraint, may be used to determine a consumer's optimal bundle of goods.
The term utility has its origins in utilitarianism, a philosophical school of thought in ethics.