Reward
A reward is getting something good for doing a given task. It needs someone who has the power to give the good thing. It is part of reinforcement that primarily deals with rewards and reliefs.
Ideas like reward unlike punishment that is based on cost and losses function based on the idea that people increase doing things to get rewards or to avoid things. In philosophy there is another idea that says that training and discipline (conditioning) are much more important than the rewards or punishments given by others.
Apart from psychology, rewards are also used on a societal scale to motivate public behavior.
In trying to catch criminals and other bad people, the government often offers money to people. This money is given to people who may capture the criminal, or give information that helps the police catch them. For example, after the Eureka Stockade rebellion in Ballarat, Victoria in 1854, the government offered a big reward of 400 pounds for the capture of the people who had started it.
In 2001, the US government offered a big reward of 2.5 million dollars for help in capturing the person who had sent anthrax in letters to a newspaper journalist and 2 senators. Anthrax is a disease which can kill people.