There's a minimum price a bidder needs to bid (Reserve Price) in order to trigger the start of an auction.
Once the Reserve Price has been met the Auction Countdown Timer will start and that bid is LOCKED. The bidder cannot remove it after the Auction Countdown Timer has started. The only way their bid can be returned is if someone else bids higher or someone purchases the piece at the full Buy Now Price before the Auction ends
If someone else comes in and bids a higher amount before the timer has ended the timer will reset to the full amount. For instance, if you set the timer for 24 Hours, the countdown would reset to a full 24 Hours when the new bid came in.
This continues until the countdown fully runs out and at that point the highest bidder is the owner.
The final step is to "Settle the Auction" this will transfer the NFT from the auction contract to the auction winners wallet. Either the seller or the buyer can pay to settle the auction. (Note: the NFT will transfer to the winner of the auction regardless of who settles the auction. It can only go to their address now.)
Note: The very first time you create an auction, you must grant the auction contract permission to interact with your tokens. Click here for more details.