This BEST illustrates the value of Positive reinforcement.
When a person is rewarded something for doing certain tasks it refers to Positive reinforcement. This is given because for rewards that person will be doing these actions. The rewards that are given for their actions acts as a a reinforcing stimulus. For instance consider that a dad gives his daughter some gifts for doing some actions or for good deeds.
In the given example, the project that has been completed by you by working day and nights and you receive a bonus cheque from your boss after two weeks. This acts as a reward for your work and motivates you to further work happily. This bets illustrates the value of Positive reinforcement.