I have discussed pods in the previous blog. Now in the short, a container is a standard unit of software that packages up code and all its dependencies in a virtualized environment that has its own file system.
As nodes are the VM or Physical Machine we could have run the container inside it without having the pod abstraction. But there will be some major problems that will arise in terms of managing the cluster and that is networking.
As we all know the container application runs in a specific port and more than one application can’t occupy a port. So if you need two containers of the same application running in a node then the same application needs to run in a different port and connection between them will be very messy.
And that is why Kubernetes solves the problem with pod abstraction. Each pod has a unique network namespace. This means each pod will have its own virtual ethernet. It’s like the pod is a small VM inside the node. And now each pod will have the application container running with the same port and there will be no conflict because all the containers running in self-contained isolated machines.
Now suppose a pod has more than one container(The main container and a helper container) then the container inside the pod will communicate with each other using the localhost.
Aniruddha Basak 