In the United States the Federal Reserve sets a target range for the federal funds rate, the overnight rate banks charge each other. Everything else, from mortgages to corporate borrowing to the discount rate applied to future company earnings, is built on top of it.
Rates move asset prices through discounting. A higher risk-free rate lowers the present value of cash flows that arrive years from now, which is why long-duration assets, meaning fast-growing technology companies as well as thirty-year bonds, fall hardest when rates rise.
The expected path matters far more than the current level. Markets price the next two years of policy continuously, so a decision that matches expectations barely moves anything and a shift in the language around future decisions can move everything.