Assets consist mostly of Reserve Bank Credit (RBC)— Treasury and Agency debt owned by the Fed, including repos

Liabilities consist of Currency in Circulation plus other capital, and together with reserves equals Assets

Monetary Base is roughly all of the currency (printed Federal Reserve Notes) plus Reserves on deposit at the Fed (ledger entries of bank reserves)

Required reserves are a fraction of Checkable Deposits, thus fractional reserve banking

Since 2008 there has been a pile of excess reserves, mostly kept on deposit at the Fed for interest

Before 2008, the Monetary Base consisted almost entirely of currency, with reserves only playing a small part

M1 is mainly the sum of checkable deposits and currency outside the banks