Here's a really simple example of a project that I had set up using docker.

For my website I have it set up with continuous integration to run my tests when I merge into master and build a docker image which it then pushes to the docker registry. I then have it ssh into my host server, pull that image, then run the new container and remove the old one.

Boom, i've just deployed my website by simply merging a PR into my master!

This is just a simple use case, and I probably wouldn't suggest deploying a production ready site like this, but it's really cool! It's really simple to just pass around images and have things up and running on local dev's too