A more thorough explanation:

Definition: The highest auction bid or the lowest bid by a qualified bidder in the letting of a contract.

Examples:

• At an auction, the best bid is the highest amount of money offered for an item.
• When a contract is being awarded, the best bid is the lowest price offered by a qualified bidder.

These examples illustrate that the best bid is either the highest or lowest amount of money offered, depending on the context. In an auction, the best bid is the highest amount of money offered by a bidder. In a contract, the best bid is the lowest price offered by a qualified bidder.