Perception refers to how our senses interpret what we take in from the environment. Our perception can be tricked by optical illusions, where our brains perceive something that is not real. There are several factors that influence our perceptions, including the object we are perceiving, our surroundings, and our own unique experiences. The document goes on to provide numerous examples of optical illusions, including images that trick our visual system into perceiving shapes, patterns, or movements that are not actually there. Many of the illusions explore how grouping and perspective influence what we see.