Ad share code on profile?

I found "Ad share code" when trying to edit the my own Profile. What the heck is that for?

Here's note on it
Your ad share code must be a url to a page that has a 468 x 60 pixels ad.
Make sure to put target=_top to all your ad links, because your ad will be placed on an IFRAME tag.
You are not allowed to have an ad that promotes adult, or at any term illegal sites

Now I get it, it's an ad revenue sharing as shown on top of forum

Strange.