Consumer choice is what derives demand Consumer choice is what derives demand. Utility theory is a basis for understanding consumer choice. Utility is a measure of satisfaction. Total Utility is the total satisfaction a consumer derives from consumption.
Utility is subjective.
It is not the same to all people. Marginal Utility is the change in total utility resulting from a one-unit change in consumption. Law of diminishing marginal utility is the notion that the more of a good that is consumed in a period of time, the smaller the increase in total utility from consuming one more unit. Your preferences are effected by your experiences, religion, up bringing, personality. We just want to how your preferences influence your economic behavior.