Discussions In Groups Viewed By Collectors?

Do "Collectors" have to join a group to have access to Discussion Threads within a group? I recently joined a group that routinely moves images from the Images tab and into a Discussion tab,and just wondering how that works,since moving it from Images removes it from the group.Answer; No they don't.It's actually a cool idea for a group. Check it outhttp://fineartamerica.com/groups/collectors-gallery.html