Visual Illusions- images or photographs that are perceived differently than they actually are. The eyes send information to the brain which fools one into seeing and perceiving something that does not line up with reality
Examples- 1. This images appears to be moving, regardless of the fact that it is just an illustration
http://www.funnyzone.org/optical-illusions/3d-wave-optical-illusion/

2. This illustration tricks the brain because it is difficult, if not impossible, to find the outlines of all of the legs. Rather, they blend into one another, creating a visual illusion.
http://sharpbrains.com/blog/2010/10/27/test-your-brain-with-these-top-10-visual-illusions/

3. This illusion tricks the brain because it is difficult to tell whether the cube in the middle is a cube coming out or a space going in, again, making this drawing a visual illusion.