Utility is measure of satisfied preference or overall happiness. An abstract measure of utility is called a util, or utilon. It is an arbitrary quantity, but can be consistently assigned once a set of utility functions are defined. All utils are equal; any diminishing returns or other factors are accounted for when utils are measured. Utils are not to be confused with hedons, units of subjective pleasure, or fuzzies, the warm feelings associated with the belief that one has accomplished good. One common denominator for utility, specially in economics, is money: the price a person is willing to pay for the satisfaction of his preference. In most contexts money can be seen as the unit of caring.
Utilitarianism is the philosophy that advocates whatever action produces the greatest amount of utility is the moral action.