Applications that cannot communicate with each other or are not accessible to end-users are worthless. Only once the communication paths are established, can applications fulfill their role.
Pods are the smallest unit in Kubernetes and have a relatively short life-span. They are born, and they are destroyed. They are never healed. The system heals itself by creating new Pods (cells) and by terminating those that are unhealthy or those that are surplus. The system is long-living, Pods are not.
Controllers, together with other components like the scheduler, are making sure that the Pods are doing the right thing. They control the scheduler. We used only one of them so far. ReplicaSet is in charge of making sure that the desired number of Pods is always running. If there's too few of them, new ones will be created. If there...
