Foreign exchange reserves are foreign currency assets held by a country's government, which are mainly used to stabilize its currency exchange rate, repay foreign debts, promote international trade and maintain national financial stability. The main purposes of foreign exchange reserves are as follows:

1. Stabilize the local currency exchange rate: When the foreign exchange market fluctuates, the government can use foreign exchange reserves to intervene in the market and buy or sell foreign currencies to maintain the stability of the local currency exchange rate.

2. Repayment of foreign debt: Foreign exchange reserves are the guarantee of a government's foreign debt. When the government needs to repay its foreign debt, it can use foreign exchange reserves to pay for it.

3. Promoting international trade: Foreign exchange reserves help to promote the development of international trade, provide means of payment for imported goods and services, and provide financial support for domestic enterprises to invest abroad.

4. Maintaining national financial stability: Foreign exchange reserves help to maintain national financial stability and enhance the ability to resist financial risks. When the domestic economy is in crisis, the government can use foreign exchange reserves to stabilize the domestic financial market.

5. Improve international status: Foreign exchange reserves are the embodiment of a country's economic strength, and having sufficient foreign exchange reserves can improve the country's status and influence in the international community.

It should be noted that excessive dependence on foreign exchange reserves may also lead to some problems, such as currency mismatch and uneven resource allocation. Therefore, when the government manages and uses foreign exchange reserves, it needs to fully consider all factors in order to achieve sustainable economic development.