Docker works same as virtual machine. But its surprisingly fast since it use host OS for computation rather running as complete separate virtual machine.

To learn docker, first you need to learn basics about docker architecture and docker life cycle. There are lots of materiel out there to learn it. Apart from that, you can follow interactive tutorials such as Katacoda to practically try out. It's really help me to learn both Docker and K8s. They have lot's of tutorials available to learn Docker and you can also contribute to create tutorials.

Tutorials like these can help :)

First of all, start using it.

The easiest way to learn something, be it a computer program or a tool like a drill, is to start using it. Obviously you will need some safety instructions and basic terminology first, so start there: read some beginner tutorials and try to understand how things are interconnected.

When you fired up some useful containers, you may want to get into deeper details. You should start reading the official documentation on different topics like how process separation works, how network packets get into and out of the containers, how disks are used and so on.

Later, if you want to become the best of the best, you will have to read technical papers, then learn Go and analyse the source code.

It all depends what type of “pro” you want to be. But regardless of that, you have to start with the basics.