In international trade it is almost impossible to mach payment with physical delivery (实际交货) of the goods, which constitutes conflicting problems for trade, since the exporter prefers to get paid before releasing the goods and the importer prefers to gain control over the goods before paying the money. The letter of credit is an effective means to solve these problems. Its objective is to facilitate international payment by means of the credit-worthiness of the bank. This method of payment offers security to both the seller and the buyer. The former has the
security to get paid provided (假如) he presents impeccable（没有缺陷的）documents while the latter has the security to get the goods required through the documents he stipulates in the credit. This bilateral security is the unique and characteristic feature of the letter of credit.
“Letter of credit” is often shortened as L/C or L.C. and is sometimes referred to as “banker’s commercial letter of credit”, “banker’s credit”, “commercial credit” or simply “credit”. Modern credits were introduced 开始采用in the second half of the 19th century and had
substantial development after the First World War. The credit is a letter issued by a bank at the request of the importer in which the bank promises to pay upon presentation of the relevant documents. It is actually a conditional bank undertaking（承诺） of payment.
The operation of the letter of credit starts with the importer. He instructs his bank to issue an L/C in favor of the seller （以…为收益人）for the amount of the purchase. Here the importer is called the applicant（开证申请人）, or opener, principal etc., the bank that issues the credit is