The difference between appearance and reality is studied extensively in the field of metaphysics. According to the University of Oregon, appearances are deceptive and derivative, whereas reality is genuine. For instance, the appearance of the size of the sun from an observer on the ground is not the reality of the actual size of the sun but rather a derivative formed by the observer.
Distinguishing between reality and appearances is something that is done by everyone on a daily basis. Whether it is looking at the rainbows in the sky or watching a person perform a magic trick, people constantly discern between what is real and what appears to be real. In general, appearances are more likely to be misleading when compared to reality, which exists regardless of whether or not it is observed by someone.
According to Plato, knowledge is of reality and opinion relates to the appearance of reality. The ways in which people makes sense of the world around them comes from a combination of appearances and reality. Furthermore, Einstein's theories of relativity and advances in quantum mechanics have led some scientists and philosophers to claim that the entire universe and three-dimensional space that people perceive as reality may simply be an appearance as opposed to something that exists independently from the observer.