The Clients interface will show a list of clients and to allow the user to right click on a client to popup a context sensitive menu. The list of clients is a tree structure and will show a number of attributes from the database for each client.
The context sensitive menu will allow the user to perform commands in the console that may be run with the desired client having been identified. These commands include requesting the status of the client, and pruning or purging jobs and files from the catalog.
To understand pruning and purging, please read the Bacula documentation at the following URL: http://www.bacula.org/rel-manual/Bacula_Console.html