Federal funds rate
The overnight rate at which banks lend reserves to one another, and the Federal Reserve's principal policy instrument.
The federal funds rate is what banks charge each other for overnight loans of reserve balances. The Federal Open Market Committee does not set it by decree; it announces a target range and uses administered rates and open market operations to keep the effective rate inside that range. The published effective rate is a volume-weighted median of actual transactions.
It matters because almost every other dollar rate is priced from it. Movements pass through to short-term business borrowing, credit card and auto rates, and, less directly, to mortgages and the exchange value of the dollar. When coverage refers to the Federal Reserve raising or cutting rates, this target range is nearly always the rate in question.
What moves markets is usually not the decision itself but the expectations published alongside it and the language of the statement. Both are released on a schedule announced a year ahead, and the Beige Book that precedes each meeting is part of the same information cycle. A change in the discount rate is a related but distinct action.
What the federal government did, once a day.
One email each weekday: the rules, filings, votes and Fed decisions that actually changed something, each one linked to the document it came from.