Valve announced a handheld gaming device they are calling the Steam Deck. It is an all-AMD piece of kit powered by Zen 2 and RDNA 2 architecture chip. The specs makes the Steam Deck sounds more like the next generation consoles from Microsoft's Xbox camp and Sony's PlayStation camp too.
The Steam Deck though, as mentioned, is a handheld device with a 1,280 by 800 resolution 7-inch LCD display. While Steam Deck runs on a custom overlay for Steam, it is a Linux based device too. That also means it can run as a PC with a proper dock or any USB Type-C dock. In that mode, you can run third party apps on Steam Deck.
While not the first kind of device of its kind, Steam Deck is a one of a kind handheld gaming device that plays PC games. While it might not sound like much, the gaming device should have no problems running PC games at HD resolution. Most of handheld gaming devices running on Windows feature processors without discreet GPUs too, but none of them are made to be as thin and small as the Steam Deck at the same time.
Prices start from US$ 399 for the Steam Deck with 64GB memory module. It tops out at 512GB in SSD storage at US$ 649. While it is not going to be advisable for you to remove the back plate to swap out the SSD, the memory is expandable via Micro SD. Unlike the Nintendo Switch, the controllers are not detachable. 
While it is more expensive than the Nintendo Switch, it is a little more functional than the Nintendo Switch itself. It is also still cheaper than a gaming PC. Is it worth buying then?