Starting July 29, 2021, the interest rate on excess reserves (IOER (https://fred.stlouisfed.org/series/IOER)) and the interest rate on required reserves (IORR (https://fred.stlouisfed.org/series/IORR)) were replaced with a single rate, the interest rate on reserve balances (IORB (https://fred.stlouisfed.org/series/IORB)). See the source's announcement (https://www.federalreserve.gov/newsevents/pressreleases/bcreg20210602a.htm) for more details.
The interest rate on reserve balances (IORB rate) is the rate of interest that the Federal Reserve pays on balances maintained by or on behalf of eligible institutions in master accounts at Federal Reserve Banks. The interest rate is set by the Board of Governors, and it is an important tool of monetary policy.
See Policy Tools (https://www.federalreserve.gov/monetarypolicy/reqresbalances.htm) and the IORB FAQs (https://www.federalreserve.gov/monetarypolicy/iorb-faqs.htm) for more information.