Utils are the unit of measurement for utility, or the degree to which preferences are satisfied. They are a purely abstract unit; there is no standard definition of how much goodness constitutes one util. Unlike dollars, utilons are assumed to always be equally valuable; where there are diminishing returns, that is represented in the conversion from states into utility, not in a change in the marginal value of one util. 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.
Utils are sometimes called utilons on Less Wrong.