Dockets allows you to create containers which share same OS and resources but provide isolated environment to run different applications in different containers at the same time.  It is the new hot technology which which has seen a huge growth and adaptation by many companies around the world.

If you are interested in docker and  try it out , here is the good news  , Play-with-docker is providing  Free Docker Training for Beginners Intermediate & Advanced users . The tutorials provided are from docker and the members of docker community.

About Play-with-docker Site 

Play-with-docker (PWD) is a site made by Docker captains Marcos Nils and Jonathan Leibiusky. PWD is a Docker playground which allows you to try Docker and Swarm Mode in a matter of seconds. It gives you the experience of having a free Alpine Linux Virtual Machine in the cloud where you can build and run Docker containers and even create clusters with Docker features like Swarm Mode. Under the hood DIND or Docker-in-Docker is used to give the effect of multiple VMs/PCs.

Here is the link to free training :

Play-with-docker (PWD) Free Docker Training for Beginner, Intermediate and Advanced Users