Microsoft has officially unveiled the next major version of Windows Phone, version 8.1 which will be coming to all Windows Phone devices over the course of the year. Windows Phone 8.1 includes more customization options such as Start Screen wallpapers, and new functionality such as a notification center which brings it up to speed with other mobile platforms such as iOS and Android.
Windows Phone 8.1 also includes a brand new voice assistant, designed to take on iOS's Siri. Cortana, the name of the new Windows Phone assistant will learn about you, and will be able to perform certain tasks all by talking to it. Windows Phone 8.1 will introduce a new quick toggle feature, allowing the user to set their most used settings in a quick swipe down from the top of the screen.
Windows Phone 8.1 will be coming to all current Windows Phone 8 devices over the course of the year. You'll be able to get the Windows Phone 8.1 Preview via the Developer Preview program, which is expected to roll out a lot sooner.