Pavlov's experiment on classical conditioning involved pairing a neutral stimulus like the sound of a bell with an unconditioned stimulus of food. Through repeated associations, the neutral stimulus elicited the same unconditioned response as the unconditioned stimulus, resulting in the neutral stimulus becoming a conditioned stimulus that provoked a conditioned response like salivation in anticipation of food. The key elements of classical conditioning are the neutral stimulus, unconditioned stimulus, conditioned stimulus, unconditioned response, and conditioned response.