Understanding Half.com:   Half.com is a subsidiary of eBay, in which sellers offer items at fixed prices, usually items that have a UPC, ISBN or other kind of SKU, rather than rare, old or collectible items. The items available on half.com are limited to books, textbooks, music, movies, video games, and video game consoles.

Half provides a platform where sellers competitively "bid" against one another, based on Universal Product Code. The seller can see the average sale price and most recent sale price for any particular item to determine the selling price desired. A potential buyer sees the available inventory for any particular item and can choose the seller. This is the opposite of eBay where buyers bid against one another. The Pre-Order feature allows buyers to set a price and quality rating of a particular item they would like to buy. Sellers see the pre-order listed when they put an item up for sale and may sell it to the buyer if they agree with the buyer's price. This is the exact opposite of what happens on eBay's site.