Microsoft has released an update for Windows 8.1 in April 2014, which includes many new features like UWP apps can now be able to pin to the taskbar, the title bar is available in the UWP app, right-click menu is available for apps listed in the Start Screen etc., the updated version ISO of Windows 8.1 is available separately in the download menu.
The deleted start button in Windows 8 was restored in the taskbar, the start screen gets better with new customization options, more default UWP apps are bundled, more apps can be snaped in the screen, and many more changes are included in Windows 8.1. Changes and enhancements to software are major differences in Windows 8.1 (compraing with 8), there are not many new features.
Windows 8.1 (successor to Windows 8) was released to the public on October 17, 2013, it was available as an update for Windows 8 customers, or users who do not have a Windows 8 license can download standalone ISO file for clean installation in their PC.