Labels provide identifying metadata for objects. These are fundamental qualities of the object that will be used for grouping, viewing, and operating. 

If we want to list only Pods that have the ver label set to 2, we could use the --selector flag:

$ kubectl get pods --selector="ver=2"

NAME                                 READY     STATUS    RESTARTS   AGE
alpaca-test-1004512375-3r1m5         1/1       Running   0          3m
bandicoot-prod-373860099-0t1gp       1/1       Running   0          3m
bandicoot-prod-373860099-k2wcf       1/1       Running   0          3m
bandicoot-staging-1839769971-3ndv5   1/1       Running   0          3m

In addition to enabling users to organize their infrastructure, labels play a critical role in linking various related Kubernetes objects. Kubernetes is a purposefully decoupled system. There is no hierarchy and all components operate independently. However, in many cases, objects need to relate to one another, and these relationships are defined by labels and label selectors.