The use of reward in the learning process. Positive reinforcement, or use of reward, encourages the likelihood of a particular behaviour being repeated. Praise someone for good work, and you encourage its repetition.
Found on http://www.gerardkeegan.co.uk/glossary/gloss_a.htm
A behavior is followed by the presentation of an appetitive stimulus, increasing the probability of that behavior. Found on https://www.encyclo.co.uk/local/22842