We've been hearing a lot about the notification center for the new version of Microsoft's Operating System, Windows Phone 8.1, where the above image leaks, claiming it to be previously rumored, Windows Phone notification center.
According to the words on the reports, the new refresh to the Microsoft's Operating System will add a new notification center, a live tile (as seen in the above picture) indicating the left around notifications from various applications. This new live tile on your homescreen will simply show the number of notification pending on the device, with no specific detail, reported by the source. As we already know that, Microsoft is in plans to release a GDR3 update to their current Operating System followed by the Windows Phone 8.1 refresh, we need to be waiting for it to be official.
Source: XDA-Developers, GSMArena