The theory of operant conditioning is defined as an approach used in behavioral sciences with the purpose of creating or extinguishing a behavior based on the application or retention of stimuli.
First proposed by B.F. Skinner, it's term "operant" is described in Skinner's own words as:
"active behavior that operates upon the environment to generate consequences"
This being said, the theory argues that the modification of behavior occurs when a positive stimulus (reinforcer) is given as a motivator, or when a positive stimulus is taken away as punishment. This is commonly known as the consequence of a behavior.
Therefore, when a good behavior is rewarded, and bad behavior is not, what we are actually doing is modifying the behavior so that it would persist being good. Yet, the opposite may also occur when we either do not correct, or accidentally reward, bad behavior. Hence, there the operant conditioning theory is basically a combination of interventions of positive and negative origin whose implementation or removal would ultimately lead to a behavior to persist or desist.