"There is no option to rotate around selected, but it is planned." excellent!
Material nodes; https://docs.blender.org/manual/en/dev/render/blender_render/materials/nodes/introduction.html
Kismet nodes; https://docs.unrealengine.com/udk/Three/KismetUserGuide.html
These are examples of nodes used in different apps.
They are an easy way of producing different results for materials, animations, HUDs, UIs etc.
Nodes are used in UE2, UE4, Unity et al.