Federal Funds Rate

This is the rate the Federal Reserve sets for banks lending to each other overnight. It sounds like a niche technicality, but it's the anchor for almost every other interest rate in the economy: mortgages, car loans, credit cards, business borrowing. Raise it, and borrowing gets more expensive everywhere, which cools spending and (in theory) inflation. Cut it, and borrowing gets cheaper, which is meant to encourage spending and hiring. It's the single lever the Fed pulls most often, and markets watch every meeting where it might move.