I took this course via Pluralsight and it was a great course, it explains or gives an overview of what are containers, what you can do with a container, etc. It mentions specifically about Docker and what it is, the “container registries“, also refer a little about what is orchestration and shows some software programs that let you (“do orchestration”) manage containers in a simple way.
The course took me one hour and forty-seven minutes. Has a good rating and it is for beginners level, so it a good intro course to the containers world.
Pluralsight course link: https://goo.gl/atHNKW