Reserves
What reserve not met means, and what happens when a reserve is never reached.
A reserve is the lowest price the seller will accept for a lot. The lot page shows whether the reserve has been met or not met; the amount is never shown to anyone bidding.
If you are the high bidder when a lot closes but the reserve was not met, the lot is unsold and you owe nothing. The house may then offer it to you at a price after the close; see Second-chance offers.
Most lots have no reserve and sell to the highest bidder whatever the price.