Windows 8 is a totally new version of Windows that, in addition to the traditional desktop, also includes a new-style interface for use with touchscreens - whether that's on a touchscreen laptop, all-in-one PC or tablet.
And, while not all PCs will be touchscreen when Windows 8 launches, expect more and more devices to have touchscreens towards the new year - even if it's a traditional laptop.
Windows 7 was a big hit for Microsoft, turning things around from the troublesome Windows Vista and reminding people that the Redmond giant was not quite ready to hang up its hat just yet.
The Windows 8 release date is here and the challenge for Microsoft is how it builds on the success of Windows 7 and show that Windows can work on iPad-like tablets. But it still needs to dominate on laptops and desktops.
Windows 8 isn't a phone OS - but does share a great deal of design language and code with its sibling, the new Windows Phone 8.