A more thorough explanation:

Definition: A by-bidder is a person who is hired by the seller to bid on a property at an auction. The sole purpose of the by-bidder is to encourage genuine buyers to bid higher by creating an illusion of competition.

Example: John is selling his antique car at an auction. He hires a by-bidder to bid on his car to make it look like there is a lot of interest in the car. The by-bidder bids on the car, and other potential buyers start bidding against him, thinking that there are other interested buyers. This creates a bidding war, and John's car sells for a higher price than it would have if the by-bidder had not been there.

Explanation: The example illustrates how a by-bidder can artificially inflate the price of an item at an auction. The by-bidder's job is to create the impression that there are other interested buyers, which encourages genuine buyers to bid higher. This can be beneficial for the seller, but it is not fair to the genuine buyers who may end up paying more than they would have if the by-bidder had not been there.