Sometimes called Skinnerian conditioning, after psychologist B.F. Skinner. A type of learning where an animal must perform a behavior in order to obtain a reward.
For example: a rat is placed in a box with a lever. When he presses the lever, food is dispensed. After enough repetitions, the rat learns that if he wants food, he should press the lever.
Operant conditioning forms the basis of almost all dog obedience, whether taught using positive reinforcement or compulsion.