Final answer:
Delayed gratification is the term used to describe the act of postponing an immediate reward for a future reward.
Step-by-step explanation:
The correct term for postponing an immediate reward in favor of completing a task for a future reward is delayed gratification. This concept refers to the ability to resist the temptation of an immediate pleasure in order to achieve a more desirable outcome in the long term. A classic example is the marshmallow test, where children were offered a choice between eating a marshmallow immediately or waiting to receive two marshmallows later.