National debt is a bond issued by the state, with low risk and fixed income, which is generally higher than the bank interest rate.

Some bonds are issued by unit companies for several years.

Foreign exchange is the exchange price between one country's currency and another's currency. For example, the price between the US dollar and RMB has been appreciating and the US dollar has been depreciating, so if you buy RMB and throw dollars, you will earn the difference between them.

In my understanding, money is a currency that can be circulated, traded and exchanged, and can be proved to be effective and valuable.

If there's anything I haven't explained clearly, there's nothing I can do. You can check it online.

I wish you a happy New Year