In economics, utility is defined as the measure of satisfaction a person gets from receiving a product or service. The word ''utility'' is used to identify the level of qualitative satisfaction experienced by a person in a specific situation, particularly in buying and selling.

An example of utility is deciding whether to eat a pizza or a burger. In economics, utility is expressed in a numerical value (util). In other words, if you feel that consuming a pizza gives you 20 utils, whereas consuming a burger gives you 15 utils, you're more likely to choose the pizza rather than the burger.

According to the utility theory, as you increase your consumption of the same product over a period of time, the value of the utility decreases. Therefore, if you eat a pizza every day, you're likely to feel less satisfied each day. In addition, you may consume a lesser amount of pizza each day.