This is called the system of fractional reserve banking because commercial banks are required to only hold a fraction of their total deposits in a central bank account. In practice, if the central bank imposes a required minimum reserve ratio of, say, 0.10, then each commercial bank is obliged to keep at least 10% of its total deposits as reserves, i.e.
The Federal Reserve provides a digital dollar to commercial banks, and commercial banks provide digital dollars and other financial services to consumers and businesses.