Ordinary linear voltage regulator is to control the tube pressure drop VDO (i.e. pressure difference) of the regulating tube through the control circuit composed of output voltage feedback and error amplifier to achieve the purpose of voltage regulation. Its characteristics are: the VIN must be large 2.VOUT, and the adjustment tube works in the linear region (hence the name of the linear regulator).
Whether the input voltage changes or the load current changes the output voltage changes, through the feedback and control circuit to change the size of the VDO, the output voltage VOUT is basically unchanged.