In Kubernetes, operator is a pattern that describes a software that runs in the cluster and manages applications and their resources. Typically, operators define custom resources to expose their functionality to cluster operators, that describe the state of a resource, and the operator works to ensure that this state is reflected in the cluster.
Examples of operators are:
- cert-manager
- sealed-secrets
- prometheus-operator
References
https://www.youtube.com/watch?v=KRNlDQTeFKs
https://kubernetes.io/docs/concepts/extend-kubernetes/operator/
https://developers.redhat.com/articles/2021/09/07/build-kubernetes-operator-six-steps