Paired exposure refers to the process in which two stimuli are repeatedly presented together, resulting in the association of one stimulus with a response that is naturally elicited by the other stimulus.
Classical conditioning is a type of learning where an organism learns to associate two stimuli and anticipate events. (e.g., Pavlov's dogs associating the sound of a bell with receiving food)
A conditioned response is a learned response that occurs after being paired with an initially neutral stimulus. (e.g., salivating at the sound of a bell after it has been associated with food)