What does down payment mean?

What does down payment mean?
A "down payment" is an initial sum of money or something else of value that is paid to secure the purchase, barter, or trade for another thing of value. In effect, it is intended to ensure that the payer will pay the balance of the agreed price, or will otherwise come through on his/her/its end of the bargain. Often, if there is not payment of delivery of the remaining amount, the down payment is forfeited.