What is Pod in kubernetes. Exaplin in 15 points with image as an example

A pod is the smallest execution unit in Kubernetes

A Pod (as in a pod of whales or pea pod) is a group of one or more containers, with shared storage and network resources, and a specification for how to run the containers. 

Pods can communicate with each other by using another pods IP address or by referencing a resource that resides in another pod.

Pods are created by workload resources called controllers, which manage rollout, replication, and health of pods in the cluster. For example, if a node in the cluster fails, a controller detects that the pods on that node are unresponsive and creates replacement pod(s) on other nodes.

pods simplify scalability, enabling replica pods to be created and shut down automatically based on changes in demand.

Each Pod is meant to run a single instance of a given application. If you want to scale your application horizontally (to provide more overall resources by running more instances), you should use multiple Pods, one for each instance. In Kubernetes, this is typically referred to as replication.

The shared context of a Pod is a set of Linux namespaces, cgroups, and potentially other facets of isolation – the same things that isolate a Docker container. Within a Pod’s context, the individual applications may have further sub-isolations applied.

When a pod is created it is assigned its own unique IP address. If there are multiple containers within the pod, they can communicate between each other simply by using localhost.

Communications outside of the pod is achieved by exposing a port. Communications between pods in a cluster takes advantage of the fact that Kubernetes assigns a cluster-private IP address to every pid in a cluster, eliminating the need to either explicitly create links between pods or to map container ports to host ports. 

Once created, a Pod remains on its node until its process is complete, the Pod is deleted, the Pod is evicted from the node due to lack of resources, or the node fails. If a node fails, Pods on the node are automatically scheduled for deletion.