DOCS-664 minor edits

Author: Bob Grabar

source/faq/developers.txt

@@ -162,7 +162,7 @@ storage efficiently in such situations.
 
 - Use the ``_id`` field explicitly.
 
-  Mongo automatically adds an object ID to each document and sets it to
+  MongoDB automatically adds an :term:`ObjectId` to each document and sets it to
   a unique value. Additionally this field in indexed. For tiny documents
   this takes up significant space. To optimize, use the ``_id``
   explicitly. Take a field that is unique for the collection and store