Bond (Finance)

A bond is a formal contract to repay borrowed money with interest at fixed intervals.
Thus a bond is like a loan: the holder of the bond is the lender (creditor), the issuer of the bond is the borrower (debtor), and the coupon is the interest.

Borrowers may issue bonds to acquire funds for investments. Some governments issue bonds to finance current expenditures.
e.g. China has recently purchased $3 billion more US bonds. This means that China is lending money and the US has in return promised to return it with interest and at fixed intervals.

for more info:
Bond on wikipedia