From the ad, it looked to me like you get a iPad-esque computing device when standalone, but that it tethers and can act as a display for macOS. Just speculative of course, but in the ad they said something like, “connect to your MacBook to extend all your MacBook apps onto the Vision Pro.”

I suspect that, like the iPad, there will be ways to force it to function as a standalone device, but that the happy path will be heavily optimized towards you buying as much Apple hardware as possible.