Forum Listing modification...how is it done?

[Masked Crusader]

I have recently been browsing gaming forums to try to get some ideas for different design features to add into my own. Today I ran across a website called xoohq.com. At their forum location http://www.xoohq.com/forums/index.php, they have done something I have never seen before. If you look below some of their forums, their subforums are clearly outlined below the forum. Though the coding looks a bit disorganized with the pictures and links being misaligned, I think it looks very creative.

My question to you all is how did they do it and how do I incorporate into my site?

Thanks for your time guys.