1. Discounted bonds: Discounted bonds refer to bonds issued by bond issuers when the coupon rate is zero and the issue price is lower than the face value. When investors buy discounted bonds, they can get principal and interest income at face value when the bonds expire.

2. zero coupon bond: zero coupon bond means that the issuer does not pay any interest to investors during the issuance process, but pays all the principal and interest income in one lump sum when the bond expires.

3. Investment bonds: Investment bonds are issued by trust companies or fund management companies, mainly for institutional investors, and are investment opportunities for fixed income assets.