What's a Circle Journal?

[SalandJeff]

I keep seeing posts that mention a Circle Journal. Can someone tell me what this is?

 

[Jennasmomma]

A group of friends participate. You pick a theme for your book. You do a layout in it and then mail it to the next person by a certain date each month. You just take turns doing a layout in each others books until it ends up back at the owner