I saw on the top right corner of some link that said 'Subscribe Forum". What exactly does it do?

I believe that it subscribes your account to get an update email every time someone posts a new reply on any topic in that forum, similar to how you can subscribe to individual threads. I'm not sure of the details of how frequently you get emails, you may only get one per thread, or one for every new post, or only one between logins, letting you know that someone has posted something new.

Except, due to IGN's server configs, the whole "email from the forums" thing doesn't work too well. Not much we can do about it, unfortunately. That and this forum has been hacked to pieces with all the unofficial mods I've installed into it, so it's kinda falling apart anyway.

So, long story short, it doesn't really do anything cause it's probably broke.

Oh thanks, I don't need stuff poping in my email anyway, so I won't use it.