A docker host’s IP address helps you in connecting you to the host network from inside a Docker container. There are methods through which you could determine the Docker host’s IP address.
If you wish to know Docker inside-out, I would recommend you to take up the Docker training from Intellipaat which offers you the online training course of 10hrs with guided projects and exercises for about 20hrs to help you gain the required hands-on experience.
Also, to get started watch our YouTube video on Docker training.