It is fundamentally a 5:1 voltage divider using a 30K and a 7.5K Ohm resistor.
Keep in mind, you are restricted to voltages that are less than 25 volts.  More than that and you will exceed the voltage limit of your Arduino input.
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INPUTS :-
- GND – This is where you connect the low side of the voltage you are measuring.  Caution! : This is the same electrical point as your Arduino ground.
- VCC:  The is where you connect the high side of the voltage you are measuring
 OUTPUTS :-
S:Â Â This connects to your Arduino analog input.
– (or minus): This connects to your Arduino ground.
+: This is not connected. It does absolutely nothing.