Adobe Experience Manager (AEM), is a java based content management system that is offered from Adobe. It is also known as Adobe CQ Content Management and was previously called Day CQ5, but was acquired from Adobe in 2010. AEM is based on a content repository and uses the JCR(Java Content Repository) to access the content in the repository. Adobe Experience Manager uses the Apache Sling framework to map request url to the corresponding node in the content repository. It also uses the OSGi (Open Service Gateway Initiative) framework to internally allow modular application development.
The dispatcher is AEM’s caching and/or load balancing tool. By using the dispatcher it can also help protect your Adobe Experience Manager server from attack since it will be using cached pages. The goal of the dispatcher is to cache as much content as possible, so it does not need to access the layout engine. Load balancing is the practice of distributing computational load of the website across several instances of AEM. The benefits of using the dispatcher as a load balancing tool is so that you gain increased processing power since the dispatcher shares document requests between several instances of AEM, and to have increased fail-safe coverage. This is accomplished by if the dispatcher does not receive responses from an instance, it will automatically relay the request to another instance.