it mainly pass 2 arguments ($args, $user_id). In $args there are lots of data as array. you can add or remove any data from here. Full list can be found in https://codex.wordpress.org/Class_Reference/WP_Query#Parameters
As you are working with code, better way to search the hook in code, so that you will get clear idea what is passing and how is passing. fep_message_query_args filter located in class-fep-message.php