Annotation is a set of user-specified key-value pairs, used for specifying non-identifying metadata. With annotation acts such as normal tagging, for example, a user could add timestamps, commit hashes, or build numbers to an annotation. Some kubectl commands support the --record option to record commands that make changes to the objects. Another use case of annotation is storing the configuration, such as Kubernetes deployments (https://kubernetes.io/docs/concepts/workloads/controllers/deployment) or critical add-on pods (https://coreos.com/kubernetes/docs/latest/deploy-addons.html). The syntax of annotations is as follows:
annotations:
$key1: $value1
$key2: $value2
Namespace, name, label, and annotation are located in the metadata section of the object spec. Selector is located in the spec section of selector-supported resources, such as pod, service, ReplicaSet, and deployment.