basics.rst: minor table update for Eigen types
diff --git a/docs/basics.rst b/docs/basics.rst
index dde518a..3e07e0e 100644
--- a/docs/basics.rst
+++ b/docs/basics.rst
@@ -297,9 +297,11 @@
+---------------------------------+--------------------------+-------------------------------+
| ``std::function<...>`` | STL polymorphic function | :file:`pybind11/functional.h` |
+---------------------------------+--------------------------+-------------------------------+
-| ``Eigen::Matrix<...>`` | Dense Eigen matrices | :file:`pybind11/eigen.h` |
+| ``Eigen::Matrix<...>`` | Eigen: dense matrix | :file:`pybind11/eigen.h` |
+---------------------------------+--------------------------+-------------------------------+
-| ``Eigen::SparseMatrix<...>`` | Sparse Eigen matrices | :file:`pybind11/eigen.h` |
+| ``Eigen::Map<...>`` | Eigen: mapped memory | :file:`pybind11/eigen.h` |
++---------------------------------+--------------------------+-------------------------------+
+| ``Eigen::SparseMatrix<...>`` | Eigen: sparse matrix | :file:`pybind11/eigen.h` |
+---------------------------------+--------------------------+-------------------------------+