The main goals of developing ASP.NET 5 are as follows
.NET 4.6 which is a big framework also called desktop CLR. The Core 5 CLR is a subset of desktop CLR. It does not contain Win forms, WCF, workflow or WPF.
Development is made much faster by killing the compilation step, when you save the changes in VS editor it then automatically compiles the file you just need to refresh your browser to see the changes. Now framework ships as part of the application.
Runtime performance – Faster startup time and Lower memory consumption compare to earlier versions.
ASP.NET 5 supports seamless transition from on-premises to cloud
The real benefit of cloud comes when you use PAAS model platform as service, where Microsoft manages the machine for you like patching and iis settings etc. When your application is using too much CPU or memory then you can configure the number of nodes, in todays world if you scales the server then it may break-up because of session state. In ASP.NET 5 when you move you in-memory session state application to cloud then it works seamlessly no special code is required for serialization and de-serialization.
Another thing is configuration, where you store your sql connection and application settings. These are typically in configuration file. In new world, new provider for configuration supports environment variable, Json files or even with ini file. The recommendation is to store config values in cloud for production and web.config for the development. Now you have the scoped configuration support for the application.
Now you can run your ASP.NET applications on Mac and Linux fully supported by Microsoft core 5 framework. All the cross-platform capabilities are added to the Microsoft core 5 framework.