With window 10, Microsoft is trying to keep some of the touch and tablet features it created for Windows 8, combine them with the familiar Start menu and desktop, and run it all on top of an improved operating system with more security, a new browser, the Cortana assistant, its own version of Office for on-the-go editing and plenty of new features intended to make life simpler.
Of course, that also means it's very different to use, whether you come from Windows 7, window 8 or Windows XP. You have to look in a new place even to turn your PC off.
On top of that, Windows 10 is more than just a PC operating system; it's also what will run on Windows phones – and on small tablets as well, because a 6-inch phone and a 7-inch tablet aren't such very different devices. Microsoft is expecting people to put Windows 10 on a billion devices (which ought to encourage more app developers to at least take a look at building their apps for Windows phones and tablets, as well as for Xbox One and holo lens