It's a stereogram that's supposed to be easier on the eyes since you only have to cross half-way to get the effect. We seriously need more of these because the regular ones give me a headache.
Also, use the dots on the top to help you if you're not used to these.
There are two ways to view stereograms. If you try one of the methods on a stereogram that's intended to be viewed with the other, however, the resulting image will turn out inverted: what should be closer will be further, and vice versa.
By including three pictures like this, the creator of this image ensures that no matter which method you use, you'll always get one "correct" three-dimensional image and one "incorrect" one as a result.
