DOC: PR07 Add descriptions for Index.where parameters

Author: laymonage

pandas/core/indexes/base.py

@@ -3960,7 +3960,9 @@ def where(self, cond, other=None):
         Parameters
         ----------
         cond : bool array-like with the same length as self
-        other : scalar, or array-like
+            Condition to select the entries on.
+        other : scalar, or array-like, default None
+            Replacement if the condition is False.
 
         Returns
         -------