Apperception is the process of learning new information by relating and incorporating it into past knowledge and experience. Perception is experiencing stimuli through our senses. Apperception is taking the information from stimuli (perceptions) and relating or comparing it to information gathered in the past.
For example, a perception would be seeing a dog and thinking "There is a dog." Apperception would be seeing a dog and thinking "That dog looks like my friend Larry's dog."