A bid increment is the amount that a bid is increased to beat the current maximum bid for a particular item when a higher bid is placed by another user. When you sell with Icephorm and create a listing you can either use the built-in bid increment system set by Icephorm or you can set your own. You can view the built-in bid increment system by clicking on the increment table link.
What is auto extend?
What if a user bids the same as the buy now price?
What if two users have the same winning bid when the auction ends?