DOCSP 35719 Clarify purposes of mongodump's metadata (#119)

* DOCSP-35719 clarifying metadata output

* DOCSP-35719 archive file considerations

* DOCSP-35719 updating phrasing

* DOCSP-35719 updating phrasing

* DOCSP-35719 copy edits

* DOCSP-35719 copy edits

* DOCSP-35719 adding reference to new output format section

Author: ltran-mdb2

source/mongodump.txt

@@ -321,6 +321,22 @@ If you're using :ref:`views <views-landing-page>`:
 - To export the documents in a view, use
   :option:`--viewsAsCollections <mongodump --viewsAsCollections>`.
 
+Metadata Output
+~~~~~~~~~~~~~~~
+
+If :binary:`~bin.mongodump` outputs to a directory, the output contains
+collection metadata which includes the following properties: 
+
+- Collection names
+- Collection types
+- Collection configuration options
+- UUIDs
+- Indexes
+
+If :binary:`~bin.mongodump` outputs to standard output (``stdout``), the
+output does not include metadata. For more information, see the
+:option:`--out` option. 
+
 Metadata Format
 ~~~~~~~~~~~~~~~
 
@@ -794,7 +810,8 @@ Options
 .. option:: --archive=<file>
 
    Writes the output to a specified archive file or, if the archive
-   file is unspecified, writes to the standard output (``stdout``).
+   file is unspecified, writes to the standard output (``stdout``). An
+   archive file is a single-file alternative to multiple BSON files. 
 
    - To output the dump to an archive file, run
      :binary:`~bin.mongodump` with the :option:`--archive <mongodump
@@ -816,6 +833,13 @@ Options
    You cannot use the :option:`--archive <mongodump --archive>` option
    with the :option:`--out <mongodump --out>` option.
 
+   .. note::
+
+      If :binary:`~bin.mongodump` writes to an archive file,
+      ``mongodump`` performance can improve. For more information on
+      ``mongodump`` performance impacts, see :ref:`Output Format
+      Considerations <considerations-output-format>`. 
+
 .. option:: --oplog
 
    Creates a file named :file:`oplog.bson` as part of the