Moonlight (or Moonlight Game Streaming) is an open source client implementation of Nvidia’s GameStream that allows you to stream your games and applications from a GameStream-compatible PC to another device, be it another Windows computer, a macOS or Linux desktop, Chrome OS, or an Android or iOS device.
Stream doesn’t mean you only get to look at the game. Moonlight lets you actually play games that run on a Windows machine from another device.