The Federal Reserve's primary tool for steering the U.S. economy is the adjustment of the federal funds rate. When the Fed sets interest rates, it directly impacts the cost of borrowing money for mortgages, credit cards, and business loans.

When interest rates are low, borrowing becomes cheaper, which typically encourages businesses to expand and consumers to spend. This can stimulate economic growth and lower unemployment. However, if the economy grows too quickly, it can lead to high inflation, where the prices of goods and services rise rapidly. To combat this, the Fed may raise interest rates. Higher rates make borrowing more expensive, which slows down spending and investment, effectively cooling off the economy to bring inflation back to a target level.

There is no single 'ideal' rate, as the Fed must constantly weigh the risks of stagnation against the risks of inflation. While low rates are generally favored by borrowers and those looking for economic expansion, high rates are often necessary to preserve the purchasing power of the dollar and prevent an overheated economy. The challenge for policymakers is finding a 'neutral' rate that supports stable prices and maximum employment simultaneously. Market participants often look to Fed announcements for clues on future policy, as these decisions dictate the cost of capital for the entire financial system.