In a major move from Microsoft, ASP.Net 5 represents a full reimagining of the framework, and Visual Studio 2015 features a bevy of new tools. If you're feeling overwhelmed with all the new bells and whistles, Scott Hunter, principal group program manager at App Plat, has made a handy walkthrough.
In the above video, Hunter offers an overview of the reasoning behind Microsoft's changes and upgrades (in a nutshell: there are so many device form factors for apps these days and so much more development work is being done in a browser), then goes over the upgrades themselves. It's a good way to catch up on Redmond's big new offerings and prepare yourself for the official releases.