on auctonsniper, those are called bidgroups

when you enter your bid on ebay, everyone watching the auction knows that you're bidding and they begin counter bidding to chew away at your bid - i.e. increase the price that you will pay if you win.
When you use a snipe program, no one else knows that you're bidding at all, you bid in the last few seconds and if you win, you got the best possible price.
this thing is never on