Orchestration
An individual can rarely perform useful work alone; teams that communicate securely and well can generally accomplish more.
Just like people, containers need to talk to each other and they need help in organizing their work. This activity is called orchestration.
The current leading orchestration framework is Kubernetes (https://kubernetes.io/). Kubernetes was inspired by the Borg project in Google, which, by itself, was running millions of containers in production. Incidentally, cgroups' initial contribution came from Google developers.
Kubernetes takes the declarative approach to orchestration; that is, you specify what you need and Kubernetes takes care of the rest.
Underlying all this magic, Kubernetes still launches the Docker containers, like you did previously. The extra work involves details such as networking, attaching persistent storage, handling the container, and host failures.
Remember, everything is a process!