It's the thing that used to let me connect to a network in Windows 7 by rapidly typing win, s, n, f to open the start menu -> settings -> network -> Foobar Example VPN – without having to wait for Windows to catch up between the steps. The commands are buffered as you type and executed when the system is ready.

Of course, this doesn't work anymore in Windows 10. Now you have to wait for each bit of mysterious UI to load before you can click on to the next step.