PoliceAuctions.com
No Reserve

A no reserve auction means that the item(s) being auctioned will be sold to the highest bidder, regardless of the amount of the high bid at the end of the auction, even if it is $1, as long as the minimum opening bid is met.

Reserve

A "Reserve" refers to a minimum price set by the seller that an item must sell for the bidder to win the item. This information is typically not disclosed, other than to state that the item has a reserve. A "No Reserve" item is one where the highest bidder will win the item, regardless of the amount of the bid, as long as the minimum opening bid is met.
For example, if the minimum opening bid on an item is one dollar and there is no reserve, and the highest bid is one dollar, then the bidder would win the item for one dollar.