DOCS-790 updates and clarification for the ensureIndex reference page

Author: Sam Kleinman

source/reference/method/db.collection.ensureIndex.txt

@@ -20,6 +20,9 @@ db.collection.ensureIndex()
       characters. See the :method:`db.collection.getIndexes()` field
       ":data:`name`" for the names of existing indexes.
 
+   .. see:: The :doc:`/indexes` section of this manual for full
+      documentation of indexes and indexing in MongoDB.
+
    Creates an index on the field specified, if that index does not
    already exist. If the ``keys`` document specifies more than one
    field, than :method:`db.collection.ensureIndex()` creates a :term:`compound
@@ -47,18 +50,37 @@ db.collection.ensureIndex()
    The available options, possible values, and the default settings
    are as follows:
 
-   ==================== =================  =========
-    Option                Value             Default
-   ==================== =================  =========
-    background           true or false      false
-    unique               true or false      false
-    name                 string             none
-    cache                true or false      true
-    dropDups             true or false      false
-    sparse               true or false      false
-    expireAfterSeconds   integer            none
-    v                    index version.     1 [#]_
-   ==================== =================  =========
+   .. list-table::
+      :header-rows: 1
+
+      * - **Option**
+        - **Plugin**
+        - **Default**
+          
+      * - background
+        - ``true`` or ``false``
+        - ``false``
+      * - unique
+        - ``true`` or ``false``
+        - ``false``
+      * - name
+        - string
+        - none
+      * - cache
+        - ``true`` or ``false``
+        - ``true``
+      * - dropDups
+        - ``true`` or ``false``
+        - ``false``
+      * - sparse
+        - ``true`` or ``false``
+        - ``false``
+      * - expireAfterSeconds
+        - integer
+        - none
+      * - v
+        - index version
+        - 1
 
    :option Boolean background: Specify ``true`` to build the index
                                in the background so that building an
@@ -82,8 +104,10 @@ db.collection.ensureIndex()
    :option Boolean dropDups: Specify ``true`` when creating a unique
                              index, on a field that *may* have
                              duplicate to index only the first
-                             occurrence of a key, and ignore
-                             subsequent occurrences of that key.
+                             occurrence of a key, and **remove** all
+                             documents from the collection that
+                             contain subsequent occurrences of that
+                             key.
 
    :option Boolean sparse: If ``true``, the index only references
                            documents with the specified field. These
@@ -130,7 +154,6 @@ db.collection.ensureIndex()
      :ref:`indexes-admin-stop-in-progress-build` for more
      information.
 
-
    .. [#] The default index version depends on the version of
       :program:`mongod` running when creating the index. Before version
       2.0, the this value was 0; versions 2.0 and later use version 1.