what is the thing just beneath your avatar called. where to type it.

That would be your 'custom member title', which can be found if you go to 'My Controls' and then chose the "edit profile info" option.
But I believe that only members with 1,000 posts or more have that option, just as a little added bonus. BUT, please don't take this to mean that you need to post like a crazy person in order to get to that 1,000 mark. We don't take to kindly here to SPAMMING, and posting just in order to get your post ##s up, will result in having some deleted and time in the cooler, which will not help your case at all. The most important thing here is just to post what is relevant, helpful and friendly. Quality over Quantity is always our policy!