Two machines on the same hardware: one runs VMs, one runs containers. Then build an image layer by layer, push it, run it on three hosts, and kill a host with and without an orchestrator. Or press ▶ Guided tour.
A virtual machine carries a whole operating system, so it is heavy and slow to start. A container is an isolated process sharing the host's kernel, so it starts in moments and many fit on one machine. It runs from an image: read-only layers built from a Dockerfile, cached so a rebuild only redoes what changed, and pushed to a registry so any host can pull it. Running containers on many machines by hand is imperative and fragile; an orchestrator like Kubernetes is declarative: you state what should run, and it keeps making that true.