Couldn't for the life of me get a search match to find this one...
It's one of the blue boxes on the BGG homepage. Each of those boxes is called a "module". In the default setup, it's about halfway down on the right-hand side.
"Game Forums+" is basically a list of a bunch of recent (or active, or hot) threads from all of the different game forums for all of the different games on the site. It's a way to see a bit of everything that's going on on the site, not just for one game, but for many.
Does that answer your question, or am I missing some context?