Docker is a platform for packaging, distributing, and running applications. When you package your applications as Docker images, they all have the same shape, you can deploy, manage, secure, and upgrade them all in the same way. All Dockerized applications have the same requirements to run them: the Docker Engine running on a compatible operating system. Applications run in isolated environments, so you can host different application platforms and different platform versions on the same machine with no interference.
In the .NET world, this means you can run multiple workloads on a single Windows machine, they could be ASP.NET websites or Windows Communication Foundation (WCF) apps on .NET ...