Add a bit more docs

doc/sphinx/cython/units.rst

@@ -5,7 +5,14 @@ Python Interface With Units
 
 This interface allows users to specify physical units associated with quantities.
 To do so, this interface leverages the `pint <https://pint.readthedocs.io/en/stable/>`__
-library to provide consistent unit conversion.
+library to provide consistent unit conversion. Several examples of this interface can
+be found in the ``samples/python`` folder in the 
+`root of the repository <https://github.com/Cantera/cantera/tree/main/samples/python>`__.
+Examples that use this interface are suffixed with `_units`.
+
+The overall goal is to provide a compatible implementation of the `cantera.Solution` and
+`cantera.PureFluid` interfaces. Please see those pages for further documentation of the
+available properties.
 
 Solution with Units
 -------------------