The Batch Launcher is responsible for handling batch requests. It is a separate program that does not require an entire application to be running and so may be started by a task scheduler.
During normal operation batch requests are made using the Batch Administration interface and are listed on the database. The Batch Launcher, when run, will process all these requests, in the order in which they were added.
The Batch Launcher can also be configured to run a single request by passing command line arguments to the Batch Launcher as detailed in Invoking the Batch Launcher.
Since the Batch Launcher does not require the application server to be running, it does not perform any application level authentication. Instead it uses the data-source parameters to connect to the database.