【中文版】

国债，又称国家公债，是国家以其信用为基础，按照债的一般原则，通过向社会筹集资金所形成的债权债务关系。国债是由国家发行的债券，是中央政府为筹集财政资金而发行的一种政府债券，是中央政府向投资者出具的、承诺在一定时期支付利息和到期偿还本金的债权债务凭证。

国债不仅是国家筹集资金的一种手段，更是国家调节经济的重要工具。通过发行国债，国家可以扩大财政支出，刺激经济增长。同时，国债还可以调整货币供应和利率水平，进而影响整个经济活动。

国债的种类很多，根据偿还期限的不同，可以分为短期国债、中期国债和长期国债。短期国债通常在一年以内到期，中期国债在1年至10年到期，而长期国债则通常在10年以上到期。此外，根据资金用途的不同，国债还可以分为赤字国债、建设国债和战争国债等。

近年来，随着中国经济的发展和财政状况的改善，国债市场逐渐成熟，国债的发行和交易也日益活跃。同时，为了更好地满足投资者需求和降低发行成本，国债的种类和期限结构也在不断丰富和优化。

【英文版】

National debt, also known as government bonds, is a debt-credit relationship based on the government's credit and issued to the society to raise funds. The national debt is a government-issued bond that is a promise by the central government to pay interest and repay the principal to investors.

The national debt is not only a means for the government to raise funds, but also an important tool for adjusting the economy. Through the issuance of national debt, the government can expand fiscal expenditure and stimulate economic growth. At the same time, the national debt can also adjust the money supply and interest rates, thereby affecting the entire economy.

There are many types of national debt, including short-term, medium-term, and long-term national debt. Short-term national debt usually expires within one year, medium-term national debt expires within 1 to 10 years, and long-term national debt usually expires after 10 years. In addition, there are different types of national debt based on the purpose of use, including deficit national debt, national debt for construction, and war national debt.

In recent years, with the development of China's economy and the improvement of its fiscal situation, the national debt market has gradually matured, and the issuance and trading of national debt have become increasingly active. Meanwhile, in order to better meet investors' needs and reduce issuance costs, the types and maturity structures of national debt have also been continuously enriched and optimized.