Sensation as the processing of senses by the sensory system.
In psychology, sensation and perception are stages of processing of the senses in human and animal systems, such as vision, auditory, vestibular, and pain senses. These topics are considered part of psychology, and not anatomy or physiology, because processes in the brain so greatly affect the perception of a stimulus. Included in this topic is the study of illusions such as motion aftereffect, color constancy, auditory illusions, and depth perception.
Sensation is the function of the low-level biochemical and neurological events that begin with the impinging of a stimulus upon the receptor cells of a sensory organ. It is the detection of the elementary properties of a stimulus.
Perception is the mental process or state that is reflected in statements like "I see a uniformly blue wall", representing awareness or understanding of the real-world cause of the sensory input. The goal of sensation is detection, the goal of perception is to create useful information of the surroundings.
In other words, sensations are the first stages in the functioning of senses to represent stimuli from the environment, and perception is a higher brain function about interpreting events and objects in the world. Stimuli from the environment are transformed into neural signals which are then interpreted by the brain through a process called transduction. Transduction can be likened to a bridge connecting sensation to perception.
Gestalt theorists believe that with the two together a person experiences a personal reality that is other than the sum of the parts.