There are plenty of simple examples of how the Random Effector works online and in the Cinema 4D documents. This example walks through a more complex idea, shows how to fix a typical problem and how flexible the Random Effector is for creating complex animations pretty easily.

If you are following the Step by Step tutorial, here are the steps in order:
Polygon Modeling
Joints
Cloner Object – Introduction
Cloner Object – Using Object Mode to animate
Target Effector
Optimizing Mograph Cloner for Display speed
Random Effector
Timeline
FCurve Offset to Delay Loop start
Specular and Diffuse Maps
Transparency Absorption
Refining Lights and Visible Volumetric settings