Two things going on here:
- Using USB-C to connect your phone to a screen (which can charge your phone as your phone drives the display)
- Responsive Design going beyond websites into apps so that now one app can run anywhere
There is also a third thing which hasn’t been explored much and that is “dual screen” which means your phone screen can be doing something different from the big screen it’s attached to. This whole idea is certainly not new, but all the previous attempts have failed. If this works (requires new hardware that has not been announced yet) Microsoft will have pulled off something truly great – a bunch of dumb screens driven by one smart device.