A Japanese auction is a form of auction.
The main characteristic of a Japanese auction is that buyers (bidders) must bid on each of the levels to remain active in the auction for the product. For example, if the initial bid for a good is € 25, all bidders must bid for € 25. If the next bid is € 30, and a bidder does not bid with € 30, the bidder can not continue within the auction, even if you want to bid for more than € 30.
The auction continues until only one buyer remains.