Bonds are creditor's rights and debt certificates that the government, financial institutions, industrial and commercial enterprises and other institutions want to issue to investors when they directly borrow money from the society to raise funds, and promise to pay interest at a certain interest rate and repay the principal according to agreed conditions. The essence of a bond is a certificate of debt, which has legal effect. There is a bond-debt relationship between bond buyers and issuers, the issuer is the debtor and the investor (or bondholder) is the creditor. As an important means of financing and financial instruments, bonds have the following characteristics:

(1) repayment. Bonds generally have a repayment period, and the issuer must repay the principal and interest according to the agreed conditions.

(2) liquidity. Bonds are generally freely convertible in the circulation market.

(3) Safety. Compared with stocks, bonds usually have a fixed interest rate, which is not directly related to the performance of enterprises, with relatively stable returns and less risk. In addition, when the enterprise goes bankrupt, the bondholder's claim for the remaining property of the enterprise has priority over the stock holder. (4) profitability. The profitability of bonds is mainly manifested in two aspects: first, investing in bonds can bring interest income to investors regularly or irregularly; Second, investors can use the changes in bond prices to buy and sell bonds to earn the difference.