The communicator is the device in the Hue system that is designated to control all other lights in the entertainment setup. It is either a Hue light or the Hue bridge basically which can acts as a broadcaster of the entertainment commands.
Selecting the communicator manually will only show the lights which support richer color version bulbs (E26/E27/E12/E14/GU10 and BR30), Hue Go and Hue Lightstrip Plus. These lights have hardware optimized to run entertainment smoothly.
