What is the primary mechanism to identify grouped objects in a Kubernetes cluster?

Custom Resources extend the Kubernetes API with new object types but are not the primary mechanism for grouping *existing* objects.

Labels are key/value pairs attached to Kubernetes objects, such as Pods and Services, which are used to organize and select subsets of objects for management and operational purposes.

A Label Selector is used to *query* and filter objects based on their labels, rather than being the mechanism that identifies grouped objects itself.

A Pod is a specific type of Kubernetes object, representing a single instance of a running application, not a mechanism for grouping multiple objects.