This group contains the Instance Info node. It allows access to all information regarding the current hit point for instances.
First let’s define what a “spot” is. A spot is just a spot - a fleck, a pinpoint. You can think of a spot as a single element area that is calculated or evaluated, on a surface and that it is arbitrary in size. Any given spot contains several types of data including color, normal angle, the direction that a ray is coming or going from relative to that spot, and so on. Remember Node Editor is a surface texture and shading editor so the word spot here pertains to the spots of an object’s surface. Spots are a useful primitive type for texture design, because, in general, the relations between features of the spot and features of the texture are straightforward.
This node gives control over instances - virtual polygons. I can be used to gain an ID Index for a particular instance, or get a Fixed Random index number for a non-specific instance.