https://arstechnica.com/gadgets/2017/08/laptop-external-graphics-card-review/

The external graphics card (or eGFX), long the pipe dream of laptop-touting gamers the world over, has finally come of age. Thanks to Thunderbolt 3—which offers up to 40Gbps of bandwidth, the equivalent of four PCIe 3.0 lanes—consumers finally have access to enough bandwidth in a universal standard to make eGFX a viable option.

So the theory goes, you can now take most laptops with a Thunderbolt 3 port, plug in a box containing a power supply and your GPU of choice, and enjoy better visuals and higher frame rates in games, and faster rendering in production tasks. You can even whack a PCIe video capture card or a production-ready audio interface in that external box, if you so wish.