Kubernetes is built around reconciliation: describe what you want, and controllers work to make reality match.
Desired State
Objects like Deployments and Services are declarations. They say what should exist, not exactly which imperative steps to run.
Actual State
The cluster constantly changes: pods crash, nodes disappear, and rollouts begin. Controllers watch these events and respond.
Reconcile, Don’t Script
A good controller can run the same reconcile function repeatedly and converge safely without depending on a perfect event history.