- GND -> negative
- VCC -> positive (voltage/current depends on sensor)
- AOUT -> analogOut, goes to a analogInput if you want to read the sensor that way. Pay attention that arduino can read at max AREF volt, by default AREF = AVCC = VCC = 5V (please note, taht is vcc of arduino, not of the sensor)
- DOUT -> digitalOut, goes to a pin depending on protocol used, because it is one wire, it can be something like "OneWire",
Voltage and current needed by VCC, and voltage/current ouputted by AOUT and protocol used by DOUT can be extrapolated only by datasheet.
Please note on image he use a arduino nano that exista at 3.3V and 5V, also seems wrong as these kind of sensor normally use a lot of current, witch arduino alone cannot supply
Since it is a MG811, a bit of google search give that tutorial: http://sandboxelectronics.com/?p=147