A central bank policy rate is the interest rate at which a country's central bank lends money to commercial banks, typically overnight. In India, this is called the RBI's repo rate; in the United States, it is the federal funds rate. Because commercial banks borrow from the central bank at this rate, it becomes the foundation for nearly every other borrowing cost in the economy — from home loans and business credit to government borrowing. When the central bank raises this rate, borrowing becomes more expensive across the board; when it cuts the rate, borrowing generally becomes cheaper.

When a central bank changes its policy rate, the effects travel through loans, bonds, currencies, and equities — often before the change even occurs.

The transmission from this single rate to broader markets happens through several channels. Bond markets are often the first to react, because government bond yields tend to move in the direction of expected policy rates. Today's news about Indian government bond yields rising on concerns over supply and RBI's liquidity stance is an example of this in action — when investors anticipate tighter conditions or higher rates, they demand a higher yield to compensate, and existing bond prices fall. Equity markets are also affected, because higher borrowing costs can reduce corporate profits and make fixed-income instruments relatively more attractive compared to stocks. Currency markets respond too, as higher domestic rates can attract foreign capital seeking better returns, influencing the value of the rupee against other currencies.

Today's global backdrop illustrates how widely watched central bank signals can be. Federal Reserve Chair Kevin Warsh's upcoming Jackson Hole speech is drawing attention precisely because markets are trying to read any clues about the future path of US interest rates. Similarly, the Bank of Japan's deputy governor's comments about rate-hike timing moved Japanese bond yields noticeably within a single session. For Indian retail investors, understanding this chain of cause and effect — from a policy rate decision to bond yields, loan rates, equity valuations, and the rupee — helps make sense of why markets can react sharply even to words spoken at a central banker's podium, well before any formal policy action is taken.