Finally, Zend_Layout's front controller plugin has one important feature in addition to rendering the layout: it retrieves all named segments from the response object and assigns them as layout variables, assigning the 'default' segment to the variable 'content'. This allows you to access your application content and render it in your view scripts.
As an example, let's say your code first hits FooController::indexAction(), which renders some content to the default response segment, and then forwards to NavController::menuAction(), which renders content to the 'nav' response segment. Finally, you forward to CommentController::fetchAction() and fetch some comments, but render those to the default response segment as well (which appends content to that segment). Your view script could then render each separately:
<body>
<!-- renders /nav/menu -->
<div id="nav"><?= $this->layout()->nav ?></div>
<!-- renders /foo/index + /comment/fetch -->
<div id="content"><?= $this->layout()->content ?></div>
</body>
This feature is particularly useful when used in conjunction with the ActionStack action helper and plugin, which you can use to setup a stack of actions through which to loop, and thus create widgetized pages.