Classical conditioning is a type of learning where a neutral stimulus becomes associated with an unconditioned stimulus to elicit a response. In Pavlov's famous experiment, dogs were conditioned to salivate at the sound of a bell, which was paired with the presentation of food. Over time, the bell became a conditioned stimulus that elicited the same salivation response as the unconditioned stimulus of food. Stimulus generalization can also occur, where similar stimuli to the conditioned one produce the same response. Extinction is when the conditioned response decreases and disappears without the unconditioned stimulus, but spontaneous recovery may occur later.