The term sensation “is the process by which stimulation of sensory receptors—the structures in your eyes, ears, and so on—produces neural impulses that represent experiences inside or outside the body.” We experience billions of sensations every minute and second, of our lives, we’re aware of some of those sensations and most of them we are blissfully unaware of. Our conscious mind chooses to ignore the ones we’re unaware of, and the ones we do know about are those that we recognize and identify. These become our perceptions; sensations that we specifically group as those that we are consciously aware of. 

Although most of us can voluntarily control where we place our attention -to a greater or lesser degree-it is our brains who unconsciously do this all the time. The brain receives more sensory information every second than it can process, so it needs to categorize and organize the remaining unattended sensations into other groups and forms. This categorization is the line of difference between sensation and perception. 

The recognition, interpretation and categorization of sensations one consciously feel is termed perception. It involves two kinds of processing- bottom-up and top-down processing. Bottom-up processing refers to the perceptions that are recognized and obtained from the output of sensations, However, the way we interpret that sensory information is largely influenced by the knowledge we already possess, our in-life experiences and our thoughts-this is referred to top-down processing. 

Seeing as our senses take in large amounts of both external and internal- stimuli, we only always select the part of the sensory stimuli we receive to organize, interpret and perceive. So primarily, we select sensory information to perceive based on prominence-which is very much influenced and determined by each individual’s visual or auditory stimulation along with their own individual flow of thought and personal beliefs- and this phenomenon of being able to focus on specific stimuli while excluding the other stimuli is called as the Cocktail Party Effect. 

Expectations also largely influence what information we choose to perceive. We organize information that we select to perceive into patterns based on proximity, similarity, and difference. We generally interpret and organize sensory information using a schema- a pattern that follows the thought or behavior which organizes categories of information and the relationships among them- which allows us to interpret the meaning for that sensory input based on past experience and knowledge. Motivation can also largely affect perception. Motivation to detect a relevant stimulus can greatly influence and shift our ability to differentiate between a real sensory stimulus and background noise. This capacity to identify a stimulus when it is present in a disconcerting background is termed  Signal Detection theory.