President Trump said he might stop buying from or selling to countries where America buys more than it sells — unless the Federal Reserve, the nation's central bank, lowers interest rates. Interest rates are the cost of borrowing money; when they're high, it costs more to borrow for a car, a home, or to run a business. When they're low, borrowing becomes cheaper. Trump appears to be linking two separate policy levers — trade rules and borrowing costs — to pressure the Federal Reserve to move rates down.