The document discusses sensation and perception. Sensation refers to the process of sensing our environment through the senses, while perception is how we interpret sensory information to make sense of our surroundings. It describes the perceptual process as a sequence of steps from environmental stimulus to perception and action. Key concepts covered include the Gestalt laws of perceptual organization, such as proximity, similarity, closure and figure-ground relationship, and various perceptual errors like selective perception and stereotyping.