I don't know anything is about XAP Deployer, I just found it here while browsing on Internet. Someone please tell me what exactly it is and why it is using?
There is an Application Deployment tool in Windows Phone 8 SDK which allows developers to deploy and test their apps. However, it allows deploying only one app at a time. The tool you've mentioned supports multiple apps at a time.
Note: Both the above programs require that your phone be developer unlocked (which can be done only if you have a Windows Phone developer account) They have no particular use for the general consumer.