Classical conditioning: 3. You have purchased a new television. When it turns on, there is a bright flash from the screen, and you find that over time, you squint as you push the on button.
Operant conditioning: 1. You are feeding a feral cat. You notice that over time, when the cat hears you open the door, it starts to approach the bowl before you even come outside or put food in the bowl.
Classical conditioning refers to involuntary responses that result from previous experiences. It occurs when you learn to associate two different stimuli. In this example, the stimuli of the flash and the behaviour of turning the TV are paired, so that when you are about to turn the TV, you get the necessary reaction (squinting) even without the stimuli (flash).
On the other hand, operant conditioning refers to the changes in behaviour that occur as a result of experiences after a response. In this case, the feral cat's behaviour is to come see you in order to get food. He gets rewarded for this behaviour, as you indeed feed him. This positive reinforcement means that it is likely to repeat the same behaviour again.