Merge pull request #181 from scrapinghub/doc-rules

Reword the introduction of the Rules page

docs/page-objects/rules.rst

@@ -6,13 +6,13 @@ Rules
 
 Rules are :class:`~.ApplyRule` objects that tell web-poet which :ref:`page
 object class <page-object-classes>` to use based on user input, i.e. the target
-URL and an output class (a :ref:`page object class <page-object-classes>` or an
-:ref:`item class <items>`).
+URL and the requested output class (a :ref:`page object class
+<page-object-classes>` or an :ref:`item class <items>`).
 
-Rules are necessary if you want to use an item class as output class, because
-they indicate which page object class to use to generate a given item class.
-Rules can also be useful as documentation or to get information about page
-object classes programmatically.
+Rules are necessary if you want to request an item instance, because rules tell
+web-poet which page object class to use to generate your item instance. Rules
+can also be useful as documentation or to get information about page object
+classes programmatically.
 
 :ref:`Rule precedence <rule-precedence>` can also be useful. For example, to
 implement generic page object classes that you can override for specific