Pod is the smallest deployable unit in Kubernetes. It can contain one or more containers. Most of the time, we just need one container per pod. In some special cases, more than one container is included in the same pod, such as Sidecar containers (http://blog.kubernetes.io/2015/06/the-distributed-system-toolkit-patterns.html). The containers in the same pod run in a shared context, on the same node, sharing the network namespace and shared volumes. Pod is also designed as mortal. When a pod dies for some reasons, such as getting killed by Kubernetes controller when lacking resources, it won't recover by itself. Instead, Kubernetes uses controllers to create and manage the desired state of pods for us.
We could use kubectl explain <resource> ...
