A reward is something nice given to a person who has done well. For example:
Reward can be a noun or a verb. As a verb, you can say:
The employee was rewarded for her hard work.
The boss rewarded the employee with an extra vacation day.
An award is a more formal recognition of a special accomplishment. Awards are usually given in public ceremonies in front of an audience (whereas rewards are typically only between the two people involved).
An award refers more to the recognition you receive. Sometimes a certificate, badge, or other small item is given to represent the award – but this simply symbolizes the recognition.
A prize is something you receive when you win a contest or game. A prize can be money, a trophy, or an object. When kids play games at an arcade, circus or carnival, they can win prizes if they get a certain number of points.