Windows Server Containers is new in Windows Server 2016, here is a nice infographic that I found useful in explaining this feature:
The full version is available here from the main Microsoft container landing page. There is an MS Ignite Presentation as well, sample slide below -
If this is all a bit too theoretical , here is a demo showing an IIS web app being moved into a container plus here is the getting started page with technical documentation with lots of further resources.