In psychology we often compare and contrast two different types of conditioning or learning: Operant Conditioning and Classical Conditioning. Within each of these are types of learning. Operant behavior (which goes along with operant conditioning) refers to behavior that "operates" on the environment or is controllable by the individual.
Operant behavior is done because it produces some type of consequence. For example, you are probably familiar with Pavlov's dog (classical conditioning) in which the dog salivated in response to meet powder. The dog couldn't control the salivation...that's classical conditioning. However, if the dog understood that by coming when called it would receive a treat, then it would be engaging in operant behavior.