Earnest money deposit
Money a buyer puts down with an offer to show they are serious about buying. An escrow agent named in the contract holds it, and at closing it is usually applied toward the down payment.
New Jersey example
Made-up example: a buyer offers $350,000 on a townhouse with a $3,500 deposit, then adds $14,000 more on the date set in the contract. The escrow agent holds the $17,500. If the sale falls through, the contract's terms on returning or forfeiting the deposit decide who gets it, and a dispute can end up in court.
Official source
Buying a home: consumer guide, New Jersey Department of Banking and Insurance
This is a plain-English summary. Rules and dollar amounts change, so check the official source or a professional before you file or sign anything.