Deployment

A Deployment tells Kubernetes how many replicas of your Pod should be running and handles keeping them that way. You describe the desired state, and the Deployment controller works to match it by spinning up new Pods, rolling out updates, or scaling down as needed.

When you update a Deployment (say, a new container image), it performs a rolling update by default: gradually replacing old Pods with new ones so your app stays available. If something goes wrong, you can roll back to a previous version. Under the hood, Deployments manage ReplicaSets, but you rarely interact with those directly.