The simple explanation is that the federal funds rate is the overnight lending rate between banks, which is an interest rate that only occurs in the same industry (accurately speaking, the US banking industry).

For example, Bank A in the United States provides short-term transitional funds to Bank B, which bears interest. This interest rate is the federal funds rate.

The bank reserve ratio is the deposit ratio of financial institutions in the central bank to ensure the needs of customers to withdraw deposits and settle funds.

For example, the amount of deposits received by Bank A is 1 100 million yuan, so some of these deposits must be turned over to the central bank for freezing and can no longer be dominated by commercial banks, assuming that 50 million yuan has been turned over. This ratio is 50%. That is, the bank reserve ratio is 50%. The remaining 50 million, commercial banks can be used for lending, investment and so on.