在读到economics  reading 27时，发现不明白什么是federal funds rate?定义上讲：The interest rate that the Fed targets is the federal funds rate, which is the interest rate on overnight loans that banks make to each other. 但是读后发现还是不太理解，主要是这个interest rate的影响是什么？对其他贷款或存款的interest rate有什么影响？它的作用又是什么？请高手指教，谢谢