Asp.net core is out there in the Microsoft ecosystem. Whereas with most frameworks you're better off finding a blog for tutorials asp.net offical website has some of the best documentation and tutorials you'll find.
It has the fundamentals of MVC, Entity framework and testing as well as information on migrating old solutions across. A lot of change has happened so its worth taking a look if your looking to upgrade to the newest framework.
ASP.NET Core is a significant redesign of ASP.NET. This topic introduces the new concepts in ASP.NET Core and explains how they help you develop modern web apps.