Three core concepts to use docker effectively: 1) Understanding the difference between images and containers, 2) understanding how to share files between the docker host and a container, 3) understanding how to map network ports from the docker host to the container. youtube 
YOUTUBE TqGSAwK9JLA 11min introduction to three key ideas of docker
Like many computer tools, what really makes the tool useful is when humans develop their own mental model of how the tool works.
Practice helps build those mental models.
See Wiki in Docker