This document provides an introduction to .NET Core, ASP.NET Core, and .NET Standard. It explains that .NET Core is a cross-platform version of .NET that is open-source and has a smaller footprint than the full framework. ASP.NET Core is the next generation of ASP.NET that is modularized, faster, and cross-platform. It uses a pipeline and middleware approach. .NET Standard defines a common language specification that both .NET Core and other platforms can implement, allowing libraries to run on multiple platforms. The document outlines how to get started with these technologies.