Complex sentence: In the United States, the federal funds rate is the interest rate at which private depository institutions (mostly banks) lend balances (federal funds) at the Federal Reserve to other depository institutions, usually overnight.
Split into simpler sentences: In the United States, the federal funds rate is the interest rate that banks charge to other banls. Private depository institutions (mostly banks) lend balances (federal funds) at the Federal Reserve to other depository institutions, usually overnight.