A queue is needed when submitting jobs, if no queue is given the SGE submits your job to your default queue. There are several queues available. Only the administrator can create others if needed. To display the available queues use the qstat or qconf command.
for i in `qconf -shgrpl` ; do qconf -shgrp $i ; done
Which queue do I use?
I you don't give a queue to run on with your job the Open Grid Scheduler will use an available queue where you have access to.
If you use the -q queue name option then you use a so called hard_queue list and that queue will be used.