中文：

央行逆回购是指央行在公开市场上购买有价证券的一种操作。具体来说，央行通过逆回购操作，向市场释放资金，增加市场的流动性。这种操作与正回购相反，正回购是央行在公开市场上出售有价证券，收回市场资金的操作。

央行逆回购的主要目的是调节市场的货币供应量。当市场流动性过剩时，央行通过逆回购操作向市场释放资金，以增加市场的货币供应量，刺激经济增长。相反，当市场流动性不足时，央行通过正回购操作收回资金，以减少市场的货币供应量，控制通货膨胀。

央行逆回购的操作通常是由央行在公开市场上通过招标方式进行。有价证券的种类可以是国债、政策性金融债券等。逆回购的期限通常较短，一般为7天、14天、28天等。

央行逆回购是一种重要的货币政策工具之一，可以帮助央行调节市场的货币供应量，稳定物价水平，促进经济增长。

英文：

Central bank reverse repo refers to the central bank's purchase of negotiable securities on the open market. Specifically, through reverse repo operations, the central bank releases funds to the market to increase liquidity. This operation is the opposite of a repo, where the central bank sells negotiable securities on the open market to withdraw funds from the market.

The main purpose of central bank reverse repo is to adjust the money supply in the market. When there is excess liquidity in the market, the central bank releases funds to the market through reverse repo operations to increase the money supply and stimulate economic growth. Conversely, when there is a lack of liquidity in the market, the central bank withdraws funds through repo operations to reduce the money supply and combat inflation.

Central bank reverse repo operations are typically conducted through tenders on the open market by the central bank. The negotiable securities can be government bonds, policy banks' bonds, etc. The duration of reverse repo is usually short, usually 7 days, 14 days, 28 days, etc.

Central bank reverse repo is an important monetary policy tool that helps the central bank adjust the money supply in the market, stabilize prices, and promote economic growth.