What is the function of a variable resistor?

A variable resistor is designed specifically to change its resistance in an electrical circuit, which allows it to control the flow of current. By adjusting the resistor, you can either increase or decrease the resistance, and consequently modify how much current flows through the circuit. This functionality makes variable resistors essential in various applications, such as dimmer switches, volume controls in audio devices, and other electronic devices where adjustable levels of electrical flow are needed.

The options involving conducting current, storing electrical energy, or measuring voltage do not accurately reflect the primary function of a variable resistor, as those actions typically involve other components like fixed resistors, capacitors, and voltmeters.