diff --git a/doc/source/merging.rst b/doc/source/merging.rst
index 72787ea97a782..3d6929081e438 100644
--- a/doc/source/merging.rst
+++ b/doc/source/merging.rst
@@ -86,12 +86,18 @@ some configurable handling of "what to do with the other axes":
   it is passed, in which case the values will be selected (see below). Any None
   objects will be dropped silently unless they are all None in which case a
   ValueError will be raised.
-- ``axis`` : {0, 1, ...}, default 0. The axis to concatenate along.
+- ``axis`` : {0, 1, ...}, default 0. The axis to concatenate along. 0 is the index
+  axis, 1 the column axis etc.
 - ``join`` : {'inner', 'outer'}, default 'outer'. How to handle indexes on
   other axis(es). Outer for union and inner for intersection.
 - ``ignore_index`` : boolean, default False. If True, do not use the index
-  values on the concatenation axis. The resulting axis will be labeled 0, ...,
-  n - 1. This is useful if you are concatenating objects where the
+  values on the concatenation axis. If the concatenation axis is 0, it is the
+  index axis, and the index column is ignored. If the concatenation axis is 1,
+  it is the column axis, and the column names are ignored.
+  The resulting axis after concatenation will be labeled 0, ..., n - 1.
+  That means that either the indices in the index column are replaced by 
+  new indices, column names are replaced by numbers etc.
+  This is useful if you are concatenating objects where the
   concatenation axis does not have meaningful indexing information. Note
   the index values on the other axes are still respected in the join.
 - ``join_axes`` : list of Index objects. Specific indexes to use for the other
diff --git a/pandas/core/reshape/concat.py b/pandas/core/reshape/concat.py
index 4040c65136617..e7c2932710f5b 100644
--- a/pandas/core/reshape/concat.py
+++ b/pandas/core/reshape/concat.py
@@ -44,11 +44,16 @@ def concat(objs, axis=0, join='outer', join_axes=None, ignore_index=False,
         Specific indexes to use for the other n - 1 axes instead of performing
         inner/outer set logic
     ignore_index : boolean, default False
-        If True, do not use the index values along the concatenation axis. The
-        resulting axis will be labeled 0, ..., n - 1. This is useful if you are
-        concatenating objects where the concatenation axis does not have
-        meaningful indexing information. Note the index values on the other
-        axes are still respected in the join.
+        If True, do not use the index values along the concatenation axis.
+        If the concatenation axis is 0, it is the index axis, and the index
+        column is ignored. If the concatenation axis is 1, it is the column
+        axis, and the column names are ignored. The resulting axis will be
+        labeled 0, ..., n - 1. That means that either the indices in the
+        index column are replaced by new indices, column names are replaced
+        by numbers etc. This is useful if you are concatenating objects
+        where the concatenation axis does not have meaningful indexing
+        information. Note the index values on the other axes are still
+        respected in the join.
     keys : sequence, default None
         If multiple levels passed, should contain tuples. Construct
         hierarchical index using the passed keys as the outermost level