Facebook - 'Promote group with an ad'?

[Alex! :)]

What does this do? I can't do it at the minute because my anti-virus software has blocked it. But i would like to know whether this suggests this group to friends, for example whe you go on Home on Facebook, sometimes in the top right hand corner of the screen, it suggests friends and groups. Will my group have this done automatically or is this what the 'promote group with an ad'

I know i haven't exactly worded this question very well, but if anybody could just tell me what this does, i would really appreciate it. What's the best way to promote my group? I see some group with hundreds of thousands of fans and thats ultimately what i would like! LOL

Please join!
http://www.facebook.com/home.php?ref=hom...626?ref=nf
ALSO, DO YOU HAVE TO PAY FOR THIS OPTION?