This effect can be utilized in many ways to simulate a somewhat 3-D environment with depth. The effect is viewed when the object is moused over, as the items within the object will appear to move with simulated depth. This could be used to simulate a crowd of people, trees in a forest, clouds in the sky, ect… It works great with many layers of photos you have isolated in Photoshop and saved as transparent .pngs, but also works great with vector images as well. You can add an unlimited number of layers, as well.

And yes, ALL parameters of this effect can be customized; including horizontal movement, vertical movement, the decay of the effect as the depth goes down, the speed at which the movement happens, and an option to have the clips be scaled according to their simulated depth. And the direction of movement can even be reversed by inserting negative values.