Use the left slider to adjust the AC line voltage and the right slider to adjust the DC current drawn from the power supply. You can also change the filter capacitance and the transformer turns ratio. Just click on the value with the mouse pointer and edit like any text field.
The transformer steps the line voltage up or down by the "turns ratio", which can be changed. One of the rectifier diodes conducts during the positive half-cycle and the other diode conducts during the negative half-cycle, allowing the filter capacitor to charge during both half-cycles. The load current slightly discharges the filter capacitor between adjacent cycles. The resulting voltage fluctuation (ripple) is one-half what it is with a half-wave rectifier.