This article is about baking normals with the Cycles Render Engine. But it also contains excerpts from our book The Cycles Encyclopedia. This is where you can get extensive information about how normals work internally and what they are used for.
Volume scattering is used to create effects like smoke, dust, clouds, sun beams (a.k.a. god rays) and similar things. This tutorial will help you understand everything about volume scatter in Cycles and how to get the effects you expect from it.