What is the practical relationship between Docker (from earlier chapters) and Kubernetes?

Docker Engine (and the docker CLI) is how you build, test, and run individual containers/images, typically on a single machine during development. Kubernetes takes those same OCI images and orchestrates them across a cluster of machines — scheduling, scaling, networking, self-healing — solving problems (multi-host placement, automatic recovery, rolling updates with traffic shifting) that Docker Engine alone, or even Docker Compose, does not address.