Merge pull request #27377 from sftim/20210401_namespace_default_label_name_tweaks

Improve docs for NamespaceDefaultLabelName

content/en/docs/reference/command-line-tools-reference/feature-gates.md

@@ -704,7 +704,8 @@ Each feature gate is designed for enabling/disabling a specific feature:
   the volume mounter.
 - `MountPropagation`: Enable sharing volume mounted by one container to other containers or pods.
   For more details, please see [mount propagation](/docs/concepts/storage/volumes/#mount-propagation).
-- `NamespaceDefaultLabelName`: Enable the API Server to create a default label `kubernetes.io/metadata.name` in all namespaces containing the namespace name.
+- `NamespaceDefaultLabelName`: Configure the API Server to set an immutable {{< glossary_tooltip text="label" term_id="label" >}}
+  `kubernetes.io/metadata.name` on all namespaces, containing the namespace name.
 - `NetworkPolicyEndPort`: Enable use of the field `endPort` in NetworkPolicy objects, allowing the selection of a port range instead of a single port.
 - `NodeDisruptionExclusion`: Enable use of the Node label `node.kubernetes.io/exclude-disruption`
   which prevents nodes from being evacuated during zone failures.

content/en/docs/reference/labels-annotations-taints.md

@@ -36,7 +36,13 @@ Example: `kubernetes.io/metadata.name=mynamespace`
 
 Used on: Namespaces
 
-Kubernetes API Server defaults this label to the namespace name during admission. This label can be used with any namespace selector, as an example with NetworkPolicy objects.
+When the `NamespaceDefaultLabelName`
+[feature gate](/docs/reference/command-line-tools-reference/feature-gates/) is enabled,
+the Kubernetes API server sets this label on all namespaces. The label value is set to
+the name of the namespace.
+
+This is useful if you want to target a specific namespace with a label
+{{< glossary_tooltip text="selector" term_id="selector" >}}.
 
 ## beta.kubernetes.io/arch (deprecated)