(DOCSP-9632): Explain PEM files

Author: Anthony Sansone

source/includes/prereqs/custom-ca-prereqs-rs-tls-only.rst

@@ -2,7 +2,7 @@
 
   .. list-table::
      :header-rows: 1
-     :widths: 60 40
+     :widths: 30 70
 
      * - PEM file purpose
        - Save File As...
@@ -11,4 +11,6 @@
      * - Each member of your replica set
        - ``<metadata.name>-<X>-pem``
 
+  .. include:: /includes/prereqs/pem-file-description.rst
+
   .. include:: /includes/prereqs/custom-ca-prereqs-naming-conventions.rst

source/includes/prereqs/pem-file-description.rst

@@ -0,0 +1,15 @@
+A |pem| file concatenates both the |tls| certificate and the Private
+Key. An example of a |pem| file would resemble:
+
+.. code-block:: text
+
+   -----BEGIN CERTIFICATE-----
+   ...
+   ... your TLS certificate
+   ...
+   -----END CERTIFICATE-----
+   -----BEGIN RSA PRIVATE KEY-----
+   ...
+   ... your private key
+   ...
+   -----END RSA PRIVATE KEY----