Docker builds and packages containers. Kubernetes schedules, scales, and manages them in production - handling deployment rollouts, health checks, auto-scaling, and service discovery across a cluster.

The unit in Kubernetes is the Pod (one or more containers sharing a network namespace). Deployments manage Pod replicas and rolling updates. Services provide stable DNS and load balancing. ConfigMaps and Secrets inject configuration. Kubernetes abstracts the infrastructure - it decides which node runs which Pod, restarts failed Pods, and scales based on CPU/memory metrics. Docker (or containerd) is the container runtime Kubernetes uses under the hood.