I know iPads (and I assume Android tablets) can be a second screen over wireless using third party software but it’s not uncompressed video with disk access last I checked.

The video compressed (how much depends on your network speed, it’s only noticeable on low bandwidth connections). And it’s far more than just video - you can copy files over the connection. Keyboard/mouse/touchscreen/stylus inputs are sent over it, and video camera/microphone data can be streamed in real time as well.

And it’s not just iPads, I do it all day every day between my desktop and laptop Mac. iPhones and Apple TVs can do it too.

It works best over thunderbolt but it’s usually done with wifi — always a direct wifi connection that bypasses your router because the amount of bandwidth required is so high that if you sent it to a router and then to a computer… your wifi would collapse under the load.