Watch this video, which explains fractional reserve banking. Be mindful that total reserves are the checkable deposits that the public has placed in a commercial bank. Required reserves are a percentage of the checkable deposits that must remain in a commercial bank as required by the Federal Reserve. Required reserves are set by the Federal Reserve to protect banks from customers running on the bank (that is, reserves protects a bank from customer panic). Excess reserves are a percentage of checkable deposits that a bank is authorized by the Federal Bank to lend out. Consequently, required reserves are deposits from which the banks earn a profit through the loan and repayment process.