ASP.NET 5 is a significant redesign. Checkout the overview on the ASP.NET site.
“ASP.NET 5 is a lean .NET stack for building modern web apps. We built it from the ground up to provide an optimized development framework for apps that are either deployed to the cloud or run on-premises. It consists of modular components with minimal overhead, so you retain flexibility while constructing your solutions.”
Reference
http://www.asp.net/vnext/overview/aspnet-vnext/aspnet-5-overview
