The Spot Info node in LW can sometimes be elusive for users newer to LWs nodal system, and seem confusing.
In essence, it does what it says on the tin, delivers info about all spots of the geometric surface... many kinds of info.
Due to this it can be difficult to imagine what will be the result of its impact visually, especially when using it to create or manipulate surface material shaders.
What is important about the node, is that what it does can only easily be explained in terms of the kind of info that is read from the surface, and often, by how that output info compares to other information, elsewhere in the shader network.
This tutorial aims to give an introduction to this node to help users understand its usefulness, and how to use it creatively, by seeing how vector information can be read using the node, and used to drive surface shading effects, based on the value of something else.
For those who've seen my various vids on the topic of rigging in LW... it might help to view this vid imagining that what Im doing is still rigging, but rigging a SURFACE.