A bond, or debenture, is a long-term debt security issued by a government body or a private company. They guarantee the payment of the original investment plus interest by a specified future date.

The interest to be paid generally depends on the quality of the issuer, expressed by its rating, the maturity, the currency and the liquidity.  For plain vanilla issues, the interest is fixed for the whole term to maturity, regardless of market fluctuations. 

Bonds are a good way to diversify your investments given the wide range of issuers in different countries and sectors. 

They are generally liquid thanks to an efficient secondary market.

Lastly, they can be used as collaterals.