A Geometry Group nodes collates individual Geometry nodes to assemble a scene or parts of the scene (figure 1). This node can be found under Geometry > Utility in the Node Graph Editor window 


geometry group

Figure 1: The Geometry Group node combines the logo with a ground plane


By default, a Geometry group node has two inputs, but you can increase or decrease the amount of inputs. The Add Input button adds a new Geometry input to the end. The Remove Input button removes the last geometry input.