Um, I don't know, really. But when you add more photos, the last will appear on my Flickr homepage, and vice versa. Also, you can see photos that I've marked "friends only" or whatever, if there are any. And you can send me Flickrmail (exciting stuff, eh?).
Like I said, I use this mainly to upload and share photos. I'm not sure how to use it to keep in touch with people in an effective manner. :P