A traditional system is typically controlled with a programmer, room thermostat and possibly thermostatic radiator valves. The programmer can switch your heating on or off at set times and the thermostat can give your house a uniform temperature. The thermostatic radiator valves give individual room temperature control.
However they can’t override the programmer and room thermostat so can only lower the temperature from the room thermostat set point if the heating is on. If the heating is off on the programmer or room thermostat they have no control.