Perception is the process by which individuals organize and interpret their sensory impressions to understand their environment. It involves selecting relevant stimuli, organizing them into a meaningful whole through processes like grouping and closure, and interpreting them based on factors like stereotyping, attribution, impressions and inferences. Perception is influenced by both internal factors like needs, personality and experiences as well as external situational factors. It underlies all human behavior as there can be no behavior without perception.