The reference component can be used to link to a certain component on a particular page. This way, you can edit the one original component on a certain page, and you only have to publish all the other pages that contain the reference component.
This can be usefull for temporary pages that share the same embed components, eg Beursrally.
Reference can be placed in all columncontrols/mainparsys. So not on fixed page templates like subhome-pages.