ECB has 3 main standard tools among others to implement its monetary policy: marginal lending facility, main refinancing operations, and deposit facility. They all reached record low in 2019.
Marginal lending facility (MLF):
Financial institutes borrow overnight funds from ECB at MLF rate, providing qualified collateral. MLF is a tool that ECB offers to the banks that have urgent needs for funds.
Main refinancing operations (MRO):
MRO rate is the rate at which ECB lends money to the banks for a week. The banks should provide collaterals, which ECB will sell back to them at a higher price in a week (aka RRP). MRO is a tool for ECB to adjust liquidity on a weekly basis.
Deposit facility (DF):
Banks can deposit their excess reserve at ECB for one night. The banks have to pay interest when the rate is negative.
ECB Main Refinancing Operation Rate2021-100.00%
ECB Deposit Facility Rate2021-10-0.50%
ECB Marginal Lending Facility Rate2021-100.25%