The JUA311 Usb to Vga Display Adapter acts as an external video card for your Mac or Pc. It allows you to add an additional monitor/display through your Usb 3.0 port. No need to open up the computer to add an expensive video card, with the JUA311 you simply load the drivers, plug in the adapter to the Usb port, then plug in the Vga monitor cable into the adapter and you are ready.