What is this .NET Core thing anyway?

Have you heard the buzz? .NET Core 2.0 is released, and with it a great compatability story with regular .NET Framework. Want to get started and don't know where to look? Or played with some old project.json projects and want to get restarted? Come journey with us through the fundamental principles of .NET Core, look at how these evolved during the development of .NET Core, and see how you can get started today building and deploying .NET Core products.