Add glossary entries for static and mirror pods (#12684)

* Add entries for static and mirror pods

* Tweak wording

Co-Authored-By: Zach Arnold <me@zacharnold.org>

* Write kubelet lower case

* Revise wording

content/en/docs/reference/glossary/mirror-pod.md

@@ -0,0 +1,22 @@
+---
+title: Mirror Pod
+id: mirror-pod
+date: 2091-02-12
+full_link: 
+short_description: >
+  An object in the API server that tracks a static pod on a kubelet.
+
+aka: 
+tags:
+- fundamental
+---
+ A {{< glossary_tooltip text="pod" term_id="pod" >}} object that a kubelet uses
+ to represent a {{< glossary_tooltip text="static pod" term_id="static-pod" >}}
+
+<!--more--> 
+
+When the kubelet finds a static pod in its configuration, it automatically tries to
+create a Pod object on the Kubernetes API server for it. This means that the pod
+will be visible on the API server, but cannot be controlled from there.
+
+(For example, removing a mirror pod will not stop the kubelet daemon from running it).

content/en/docs/reference/glossary/static-pod.md

@@ -0,0 +1,14 @@
+---
+title: Static Pod
+id: static-pod
+date: 2091-02-12
+full_link: /docs/tasks/administer-cluster/static-pod/
+short_description: >
+  A pod managed directly by kubelet daemon on a specific node
+
+aka: 
+tags:
+- fundamental
+---
+ A {{< glossary_tooltip text="pod" term_id="pod" >}} managed directly by the kubelet
+ daemon on a specific node, without the API server observing it.