Windows 8.1 Preview is the preliminary version of Windows 8.1, that despite of being presented a short time ago can already be downloaded and used before it's officially commercialized.
This update that Microsoft has prepared supposes a general improvement of its last operating system that includes customization options, better search and apps, the Windows Store, connection to the cloud and more security.
The update consists of downloading an .exe file from the Windows website that will allow you, in a matter of seconds, to update to the new version.