kubectl label
kubectl label <type> <name> key=value [--overwrite] | key-
Risk: Careful
What it does
Adds or removes a label. Selectors pick objects by labels.
When to use it
To group pods, or to switch a namespace's Pod Security level.
Example
$ kubectl label pod tray tier=frontStick a tier=front sticker on the tray.
Learn it in: Labels and selectors · Official docs