This is a recommended class for your front-end web application. App_Frontend is minimalistic, it will not add anything unless you request it to.
When referring to App_Frontend and Frontend those are being two different classes. The first of those two is a standard class by Agile Toolkit - second is a suggested name of yoru own cusom class you create in your application.
Frontend will route pages as per a simple association:
For a more advanced routing, see Controller_PatternRouter
App_Frontend also allows you to use Layout. Place this in Application init:
$layout = $this->add('Layout_Fluid'); $layout->addLeftMenu('MyMenu'); $layout->addUserMenu('UserMenu');