How to quickly learn docker?

Question

Docker

Those. I understood that these are applications in containers, but how they actually use it, i.e. let's say I have a physical server, I need to deploy several VPSs on it, and on one of them I configure each application in a docker container, then somehow connect them, somehow forward ports and configure configs, after which I deploy only those applications which are needed on other vps. Do I understand the principle of using docker correctly? They also write that docker containers will not start on different linux distros, are these statements relevant for centos6 and centos7?

Answer 1

How to quickly learn docker?

https://docs.docker.com/

Answer 2

training.play-with-docker.com