Docker isn't a Windows thing particularly - it's an open platform that runs on many OS's. In fact, my understanding is that it works less well on Windows than on Linux, but I'm no expert.
It's certainly something that's being used lots where I work, and I hear about it being used plenty elsewhere from friends working for other employers.
Essentially, it gives you the ability to run things in a temporary, isolated environment that you control, without all the overhead of running a virtual machine.
I use it in the same way as I use git - I know the commands to do the things I need to do, without being very knowledgable about what goes on under the hood :)
When this is highlighted in the Visual Studio 2017 developer's news feed, with zero prior knowledge of the concept made me kinda think this was something MS was pioneering.