The scene effects are designed to enhance the 3D compositing environment.
The parallax effect creates the illusion of 3D depth in a 2D layer.
In this example parallax has been used to apply a cracked concrete texture to some text:
The Height Map is used to determine the depth effect.
When set to None the host layer's own texture will be used for the parallax effect. You can also choose a different layer to use as the height map.
The Blur Height Map property can be used to create a softer, smoother parallax effect.