Unlike names and UIDs, labels do not provide uniqueness. In general, we expect many objects to carry the
same label(s).
1.
Via a label selector, the client/user can identify a set of objects. The label selector is the core grouping
primitive in Kubernetes.
2.
The API currently supports two types of selectors
a. equality-based (=, !=)
b. Set-based (in, notin, exists)
3.
Command of set-based: Kubectl get pods{object} -l 'env in (dev,test,qa)'