The Federal Reserve can control the supply of money by adjusting the interest rate it charges the borrowers. What is this rate called?

This interest called is the Federal Funds rate of which the bank is able to lend to other banking or depository institutions. Furthermore, this is t he interest rate that the loaning bank pays to the lending bank to borrow the amount that is negotiated between banks, and the average of this rate across all such transactions is also considered the federal funds effective rate.