With Gamestream technology NVIDIA provides a solution to wirelessly transmit a game from a Gaming-PC to a smartphone.
When using a suitable gamepad (see below) the smartphone is used for display and soundplayback as well as a sender for the gamepad inputs.
This technology brings graphical complex games to the smartphone which are processed on a powerful gaming pc.
Many graphic cards require a connected display which is turned on, otherwise the graphical output is not calculated. To get rid of a useless power consuming display you can connect a tiny HDMI adapter which can "simulate" a display with up to 4K resolution. The pc works then "headless", the In- and Output takes place on the smartphone.