diff --git a/components/css_selector.rst b/components/css_selector.rst
index 54965337765..8018b4ca675 100644
--- a/components/css_selector.rst
+++ b/components/css_selector.rst
@@ -9,7 +9,7 @@ The CssSelector Component
 Installation
 ------------
 
-You can install the component in many different ways:
+You can install the component in several different ways:
 
 * Use the official Git repository (https://github.com/symfony/CssSelector);
 * Install it via PEAR ( `pear.symfony.com/CssSelector`);
@@ -18,9 +18,71 @@ You can install the component in many different ways:
 Usage
 -----
 
-The component only goal is to convert CSS selectors to their XPath
+Why use CSS selectors?
+~~~~~~~~~~~~~~~~~~~~~~
+
+When you're parsing an HTML or an XML document, by far the most powerful
+method is XPath.
+
+XPath expressions are incredibly flexible, so there is almost always an
+XPath expression that will find the element you need, but they quickly
+become very complicated, and the learning curve is steep. Even common
+operations (such as finding an element with a particular class) can require
+long and unwieldy expressions.
+
+Many developers -- particularly web developers -- are more comfortable
+using CSS selectors to find elements. As well as working in stylesheets,
+CSS selectors are used in Javascript with the ``querySelectorAll`` function
+and in popular Javascript libraries such as jQuery, Prototype and MooTools.
+
+CSS selectors are less powerful than XPath, but far easier to write, read
+and understand. Since they are less powerful, almost all CSS selectors can
+be converted to an XPath equivalent. This XPath expression can then be used
+with other functions and classes that use XPath to find elements in a
+document.
+
+The ``CssSelector`` component
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The component's only goal is to convert CSS selectors to their XPath
 equivalents::
 
     use Symfony\Component\CssSelector\CssSelector;
 
     print CssSelector::toXPath('div.item > h4 > a');
+
+This gives output of ``descendant-or-self::div[contains(concat(' ',
+normalize-space(@class), ' '), ' item ')]/h4/a``. You can use this
+expression with, for instance, :phpclass:`DOMXPath` or
+:phpclass:`SimpleXML` to find elements in a document.
+
+.. tip::
+
+    The :method:`Symfony\\Component\\DomCrawler::filter`` method uses the
+    ``CssSelector`` component to find elements based on a
+    CSS selector string.
+
+Limitations of the CssSelector component
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Not all CSS selectors can be converted to XPath equivalents.
+
+There are several CSS selectors that only make sense in the context of a
+web-browser.
+
+* link-state selectors: ``:link``, ``:visited``, ``:target``
+* selectors based on user action: ``:hover``, ``:focus``, ``:active``
+* UI-state selectors: ``:enabled``, ``:disabled``, ``:indeterminate``
+  (however, ``:checked`` and ``:unchecked`` are available)
+
+Pseudo-elements (``:before``, ``:after``, ``:first-line``,
+``:first-letter``) are not supported because they select portions of text
+rather than elements.
+
+Several pseudo-classes are not yet supported:
+
+* ``:lang(language)``
+* ``root``
+* ``*:first-of-type``, ``*:last-of-type``, ``*:nth-of-type``,
+  ``*:nth-last-of-type``, ``*:only-of-type``. (These work with an element
+  name (e.g. ``li:first-of-type``) but not with ``*``.