Marginal utility

Marginal utility is how much we value one extra unit of something. For example, let's say we have a bag with 5 pieces of candy in it. The first piece of candy will taste the best, and because of this, it will have the most value to us. As we eat each piece of candy, the piece of candy that we eat next will have a bit less value than the piece before it - this is because we don't value it as highly as the first piece of candy we ate. This decrease in value for each piece of candy we eat is called marginal utility.