Escrow is an arrangement between two parties to a transaction and a third independent party who agrees to hold money or assets until a specific date, or until certain obligations have been met, or until the transaction is completed.
In the US, the most common use of escrow is in real estate transactions, where a mortgage lender will set up an escrow account into which the borrower pays sufficient funds to pay the property taxes and insurance premiums as they come due.
A form of escrow that is common in many countries is the payment of a deposit by a tenant to a landlord at the beginning of the tenancy, as security for unpaid rent or damage. The deposit is paid back at the end of the rental (minus any deductions).