OPERANT CONDITIONING 

Operant Conditioning involves the dog's conscious ability to act in accordance to certain given consequences. It involves mechanical movements such as sitting, moving, and restraining from action. When people think about dog training, in general they're mostly thinking operant conditioning, because most dog trainers primarily focus on teaching mechanical skills and stopping unwanted behavior through the use of the quadrants.

THE QUADRANTS of Operant Conditioning:
When people hear of Reinforcement or Punishment, they tend to tie emotional meanings to these words. Throw in the words "negative" and "positive" and you got yourself the perfect recipe for misinterpretation. Simply put, Reinforcement and Punishment are consequences that dictate whether a behavior is likely or less likely to occur in the future. The word "Punishment" tends to elicit a very strong emotional response in our brain, but in reality, it's simply a term that indicates the behavior is LESS LIKELY to occur again. On the flip side, "Reinforcement" is the consequence that ensures the behavior is MORE LIKELY to occur again, regardless of whether you're using "positive" or "negative" reinforcement, the outcome would be the same (the rate of the behavior increases). Check out this article and this article which explains why you want to use all 4 quadrants.

CLASSICAL CONDITIONING

Classical conditioning involves a different type of process. It's related to the "emotional" (if you will), responses. For instance, a neutral stimulus (thing) can have a pleasant or unpleasant effect on two different animals, including people. The sight of a person might immediately make your palms sweaty, your hairs in the back of the neck stand, your eyes dilate, or maybe even tremble in anxiety. This is a very simple and basic example of classical conditioning. There's a good chance this person at one point meant nothing to you, but as a result of some experiences, the presence of this person triggered involuntary responses. 

In dog training, we employ the use of techniques such as: Flooding, Counter Conditioning, Systematic Desensitization and Habituation to influence how a dog feels about a given stimulus or set of stimuli. This doesn't involve sitting, heeling, downing or recalling. This is the missing ingredient in many trainers' set of skills.