
A Bid Auction is where a seller sets an opening price for a product and potential buyers opt to win the product by offering a higher price (bid). This bidding process moves the price up and at the conclusion, the highest bidder wins the item.
A BIN auction is where a seller sets a fixed price for the product and a buyer can choose to pay this price and immediately win the item.
In some instances the buyer can make an offer below the fixed price giving the seller the option to accept and close the sale.