Versions of CQ before 5.5 were based on a servlet container (CQSE, by default, though others could be used) running with multiple webapps: One for the CRX content repository and one for the OSGi container which itself contained Sling and Adobe Experience Manager.
The Sling webapp was bound to the root and handled most of the request processing.
With CQ 5.5 and AEM, the OSGi container is positioned at the root and the OSGi HTTP service, backed by Sling acting as the sole request handling end point. The CRX content repository is now just another OSGi service, alongside the various services that comprise the rest of the AEM unctionality. These changes do not affect applications built on top of AEM or Sling.
The new architecture means that the quickstart jar installation of AEM can no longer support other web applications running alongside AEM. However, the war version of AEM is designed to be deployed in an application server, where additional web applications can be deployed alongside it.
Added three new connectors to key adobe products – Creative Suite, Scene7, Search&Promote
Authors can directly work on mobile apps.
Partnered with hybris software to add some nice eCommerce capabilities.
Added Undo(Ctrl+z) and Redo(Ctrl+y) functionalities.
Dispatcher is CQ5 caching and/or load balancing tool. Dispatcher also helps to protect your AEM server from attack. It cache responses from publish instance, to increase the responsiveness and security of your externally facing published website