There are only three Render effects: Clouds, Julia Fractal, and Mandelbrot Fractal. It's hard to figure out just what to do with Render effects. But, if you are geeky like me, you will love them:
Out of these three effects, Clouds is the one you will probably find the most use for. It doesn't really make clouds. What it does is render a cloud-like image based on a mathematical algorithm, which you will need an advanced math book to understand. For our purposes, you don't need to know how it does it, but just need to know what it does.
Clouds has three controls: Scale, Roughness, and Blend Mode. When you first employ it, your image will disappear completely and be replaced by some grayish clouds. Scale will give you a zoomed view of those clouds. Roughness will determine how soft or hard you want your clouds to look. It is the Blend Mode that makes things interesting.
Blend Mode will allow you to blend the clouds you create with your photos in very interesting ways. There...