We do not think of money as having an intrinsic value, more than the number printed on the face of it, but it does; it is the purchasing power of that money over time. Inflation is the enemy of money. If prices rise the value of money tomorrow will not be the same as its value today.
The central bank is tasked with trying to keep inflation low and consistent so that prices rise slowly, and if salary increases are linked to inflation, the buying power of your money is in theory, retained over time. To do this, the central bank signals to the market using their policy rate. In South Africa this is the repo rate.