An escrow is a financial arrangement where a third party holds and regulates payment of the funds required for two parties involved in a given transaction. It helps make transactions more secure by keeping the payment in a secure escrow account which is only released when all of the terms of an agreement are met as overseen by the escrow company.
Escrows are very useful in the case of a transaction where a large amount money is involved and a certain number of obligations need to be fulfilled before a payment is released.