What are the similarities and differences between classical and operant conditioning?

Both classical and operant learning are psychological
processes that lead to learning. Here learning refers to the process by which changes in
behavior, including actions, emotions, thoughts, and the responses of muscles and
glands, results from experience or practice.

Classical
learning which is also called respondent learning is based on stimulus response
relationship. The learning of this type occurs when (a new stimulus begins to elicit
behaviour similar to that originally produced by an old stimulus. For example if a dog a
bell is sounded every time a dog is given food, the dog will begin salivating in
expectation of food just at the sound of bell. Classical conditioning process is
particularly important in influencing our emotional behaviour.  For example, we often
learn to fear a stimulus that has been combined with some other frightening
stimulus.

Operant learning, also called instrumental
conditioning, takes place as a result of what happens after a response is made. For
example, if a baboon is rewarded with food every time a button is pressed, it will learn
to press the button for obtaining food. In one famous experiment displaying operant
learning, the psychologist B.F. Skinner trained rats to press a lever to get food. In
this experiment,a hungry rat placed in a box containing a lever attached to some
concealed food.  At first, the rat ran around the box randomly. In this process it
happened to press the lever, and the food dropped into the box.  The dropping of food
reinforced the response of pressing the lever.  After repeating the process of pressing
the lever followed by dropping of food many times, the rat learned to press the lever
for food.