Document Twig vs PHP types

doc/templates.rst

@@ -76,8 +76,18 @@ Twig templates have access to variables provided by the PHP application and
 variables created in templates via the :doc:`set <tags/set>` tag. These
 variables can be manipulated and displayed in the template.
 
-Use a dot (``.``) to access attributes of a variable (methods, properties
-or constants of a PHP object, or items of a PHP array):
+Twig tries to abstract PHP types as much as possible and works with a few basic
+types, supported by ``filters``, ``functions``, and ``tests`` among others:
+
+* ``string``: A sequence of characters;
+* ``number``: An integer or a float;
+* ``iterable``: A sequence, a mapping, or an iterable object;
+* ``object``: A structure supporting method calls;
+* ``boolean``: ``true`` or ``false``;
+* ``null``: The special ``null`` value.
+
+The ``iterable`` and ``object`` types expose attributes you can access via the
+dot (``.``) operator:
 
 .. code-block:: twig