This is the latest version of Windows - Fall Creators Update. it's a media creation tool that can be used to upgrade an existing installation of Windows or create installation media for another PC. Just make your choice after launching the tool and it'll do the rest.
What was new in Windows 10? The latest release brings back the Start Menu, though with a Windows 8 twist: live tiles keep you up-to-date with the latest news while also providing an easy way to launch apps. (Don't worry if you prefer the Start Screen, it's still there and you can boot into it if you prefer.)
Apps now work much more like regular desktop programs. They have minimise, maximise, restore and close buttons, and can be resized (to a degree) and organised however you like.
If you've still lost track of a program in the mass of open windows, a new Task Spaces feature can help. Click its taskbar button and you'll see thumbnails for everything running now, a little like OS X's Mission Control - just click something to switch to it.
Better still, Task Spaces also supports virtual desktops. Add extra desktops as required and it'll display thumbnails of each one, making it easy to identify whatever you're after and switch to it.
There's also smarter snapping, new customisation options, and even a bunch of experimental additions to the command prompt.
Fall Creators Update brings a whole host of new features for Windows 10. See the Microsoft Blog for more information.
The Windows 10 ISO here will give you build 1607 which is the August 2016 Anniversary Update.
It's a natural evolution for both Windows 7 and 8.1 users, bringing back the Start menu for the latter while adding useful new tools like Task Spaces, Cortana and app windowing.