Hehe, here is my “own” definition for bonds, stocks, etc.
- Zero-coupon bond: like a bank account. Buy this type of bond is similar to deposit money to bank account and earn interest. However, with a same interest, deposit $100 in a bank account means that you need to pay total $100 for a bank while a zero-coupon with face value of $100 can be bought by a lower price. So investing in bonds make more profit than send money to a bank. Instead you have a lot of money, then you should ask a bank to keep them for you and earn interest. Otherwise, take the money you have to invest to make more and more money 
English
French