How do Attachment displays attach?

Just wondering if someone could explain how Attachment displays work...? Is there any link between them and the view/display they're attached to, or if not, can this be specified somehow?

For example, I have a view displaying a map of node locations. I'd like to list other, related (via a node-reference field) nodes in each map nodes pop-up info box. It doesn't seem to be working 'out-of-the-box', so I figure I may need to specify a relationship or something to link the views together, if at all possible...

Thanks!