An illusion, as defined by dictionary.com, is a perception of stimuli that represents what is perceived in a way different from the way it is in reality. An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. Illusions can occur in all human senses, however, optical is the most common.
The childs head appears to be floating, however in reality, the child is in a box with mirrors around it.
In this illusion, one would think they are seeing jesus, when in fact all it is are a bunch of random brush strokes that make it appear to be jesus. Non-religous persons may see something entirely different.
In this illusion, most can see two images. One is an image of an elderly couple, and the other is an image of a man trying to serenade another woman.