It has a whole new design, and lots of new features! http://www.apple.com/ios/whats-new/ says the following: "iOS 7 introduces great new features like Control Center, AirDrop for iOS, and smarter multitasking. It also makes the things you do every day even easier, faster, and more enjoyable. And while many of the apps look different, the way you do things feels perfectly familiar. So from day one, you know how to use the world?s most advanced mobile OS. In its most advanced form." Go to apple.com/ios/ to read more about the awesomeness! :)
Aside from the new design, they added more features such as the control center where it gives you quick access to apps, new notification center, they added new filters to their camera for both photos and videos, they have a new photo collection where it would be easier to store pictures , they have airdrope where you can easily share files and etc.. so many features.