I'll ask Commander Mulholland to fill in the blanks on this, but essentially this is an agreement amongst allied nations to exchange an awareness of the presence of submarines and the routing of submarines so as to avoid mutual interference. Where submarines are operating in the same area it's to arrange for their separation so that there is no mutual interference during operations.
I'm not sure we can get into too many of the details of how we go about that, but in principle that's the idea. It's to make sure you don't bump into someone by accident when you're travelling around the world. When you're operating together you can do so with the confidence that there's no one else, at least no other friendly submarines, that are within the space that you've been given to operate.
Do you want to add anything to that?