What’s the "Contacts" Button for in Contact Edit for Outlook 2007?

I’ve seen this button before but never really thought about it I guess when I was editing a contact in my address book in Outlook 2007.
When you click on it, it lets you browse through all of you contacts and you can add a contact into this field.
My question is what’s it for?
Is it letting me link contacts to each other in some sort of relationship? Are there tasks and controls I can use to manipulate or view contacts by their relationships assigned in this field?
I can’t even find anything about it online when I did a quick …read more