What's the differences that bill of exchange from a contract?

A bill of exchange or "draft" is a written order by the drawer to the drawee to pay money to the payee. A common type of bill of exchange is the cheque (check in American English), defined as a bill of exchange drawn on a banker and payable on demand. Bills of exchange are used primarily in international trade, and are written orders by one person to his bank to pay the bearer a specific sum on a specific date. Prior to the advent of paper currency, bills of exchange were a common means of exchange. They are not used as often today.