Illusion is basically the mistaken visions that appears to us as reality. In actual it is the distortion of our senses and manipulation of logical thinking of human mind. A common man can easily call it as fooling of human vision and human mind. Talking about psychological impacts, it is the mistaken optical illustration which confuses human mind and keeps the clarity away from human sight making false images as true vision. Many artists have work in this field of arts and taken illusion as a scientific technique of making fine arts more alluring and captivating.
There are many examples set by various artists to illustrate illusion in their piece of art. Few master pieces are listed below. You will also like the 3d optical illusion work of Igor Eskinj.