optical illusions

[nec208]

Anyone know what is a optical illusions and how it works?

The URL is to big bu it is on the yahoo main page on optical illusions and the reply is.

Our minds try to see things in the most basic way. Upon seeing an optical illusion, we try to see basic objects or shapes, but when you look at individual parts, it doesn't make sense. Basically, it's our minds trying to find the easiest way to interpret the image

Again not saying much