What is a Pod in Kubernetes?

A Pod is the smallest unit Kubernetes schedules and runs. It wraps one or more containers that always run on the same node and share a network namespace (one IP address, so they talk over localhost) and the Pod's volumes. Most Pods have a single application container, sometimes with helper (sidecar or init) containers.

A minimal Pod

apiVersion: v1
kind: Pod
metadata:
  name: web
  labels:
    app: web
spec:
  containers:
    - name: nginx
      image: nginx:1.29
      ports:
        - containerPort: 80

You rarely create Pods directly: a Deployment (through a ReplicaSet), StatefulSet, DaemonSet or Job creates them from a Pod template and replaces them when they fail or when a node goes away. Pods are disposable and get a new name and IP when recreated, which is why traffic goes through a Service.

Pod phases

CrashLoopBackOff and ImagePullBackOff are not phases but container states (reasons) shown by kubectl get pods; kubectl describe pod NAME shows the events behind them.