Earnest money shows the seller you are a serious buyer
Typically when an offer to purchase a house is made, you, as the buyer, will also submit with the offer an “earnest money deposit" (EMD). This EMD shows the seller that you’re serious about buying the home and makes the offer to purchase on the property binding once accepted.   

In the event the sale doesn’t close, the sales agreement generally spells out the conditions under which the potential buyer would receive back or have to forfeit the earnest money. Generally, if the buyer does not satisfy or fulfill all the terms of the contract, when they are able to do so (a breach of contract), the seller will be in most circumstances legally able keep the earnest money as liquid damages. If the seller does not meet the terms of the contract, you, as the buyer, may receive a total or partial refund of your earnest money deposit.