Utility is the amount by which preferences are satisfied. 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.
Utilitarianism is the philosophy that advocates whatever action produces the greatest amount of utility is the moral action.