An Order Bump is a type of One-Time Offer (OTO) Product. The Order Bump typically appears as a promotional item (unselected by default) on an Order Form or on the check-out page of your web store's shopping cart. There is usually some small promotional content on the page emphasizing that this is a one-time offer for this product at this price. If the shopper selects the option to buy, then the OTO product is automatically added to the cart at final checkout.
You can also set an Order Bump to appear on the Thank You page of an Order Form, or of a web store shopping cart to catch an impulse buy on last time.
NOTE: an upsell product used as an Order Bump can only appear on an Order Form or on the Check-out page of your web store's shopping cart.