The official documentation is at: http://docs.alfresco.com
Alfresco System Receiver
The ASR is one of the 'deployment servers' for Alfresco. (The other being the file system receiver FSR).
The ASR is built into the Alfresco server and publishes a WCM web project into a (probably remote) live AVM repository. The content deployed to the live AVM repository has the benefit of Alfresco content management features such as Lucene based queries, versioning, REST based access (via Web Scripts), etc.
In order to connect to an ASR several TCP ports need to be open, 50500, 50501, 50502.
The ASR ensures that only the changes between versions are transmitted.
The result of a deployment is a runtime version of the web site. This consists of a single AVM store matching the name of the web project's AVM Store Root/DNS name property.
From Alfresco 3.2 onwards the WCM Deployment Engine and the AVM Deployment Target replaces the receiver part of the ASR. In version 3.3 the option to create an ASR configuration has been removed, although existing ASRs will still work. ASRs will be removed in some future version of Alfresco.
CIFS can be used to browse the contents of the destination server, again using the example from the screenshot, navigating to \\liveserverA\AVM\alfresco\HEAD\DATA\www\avm_webapps\ROOT would show you the contents at the root of the web project. The CIFS path can be assigned a drive mapping, that is, Z:\ or a mount point, that is, /mnt/alfresco and then used to serve the website via Apache or the webserver of your choice.
Alternatively, to browse or virtualize the deployed website on the destination server, the web client can be used to create a web project before a deployment is attempted. The only requirement is that the DNS name used during the creation of the web project is the same as the web project on the source (authoring) server. The deployment will then use the store created by the web project and thus allow all the familiar web client actions.
By default the live AVM/WCM stores are not shown in the Alfresco explorer interface. This can cause confusion for new users of Alfresco.
The visibility of the AVM/WCM stores is configured via the File Server Subsystem
Here is a snippet of configuration which shows the live Stores.
See also ASR Performance Optimization