You might want to ask vbulletin questions over at vbulletin.com as I cant tell you how to use vbulletin real indepth like they can. I can tell you the basics.
Now my observations here.
1. vbulletin does not show categories like what your posting. That to me looks like a vbulletin modification to show subforums under a parent like that. That much I know
2. You can make in vbulletin when you create a new forum for it to link to a specific url instead of it being a vb
forum so this is what that user has done for all those categories. For instance he is creating forum and subforums for his gallery but as you see they are all links to the gallery. You do that under the vb
admin forum manager. You will see the option to enter a url to act as the forum in vb
admin. See I did that for instance on my sites for sale or trade here Reeftalk Forums
3. The example your posting is vbgallery so your gallery being photopost pro will be different.