The Light Dependent Resistor (LDR) or also popularly known as Photoresistor is just another special type of Resistor and hence has no polarity so they can be connected in any direction.
They are breadboard friendly and can be easily used on a perf board also.
The symbol for LDR is similar to Resistor but includes inward arrows as shown above in the LDR pinout diagram.
The arrows indicate the light signals.
A photoresistor or LDR (Light Dependent Resistor), as the name suggests will change it resistance based on the light around it. That is when the resistor is placed in a dark room it will have a resistance of few Mega ohms and as we gradually impose light over the sensor its resistance will start to decrease from Mega Ohms to few Ohms.
This property helps the LDR to be used as a Light Sensor. It can detect the amount of light falling on it and thus can predict days and nights. So if you are looking for a sensor to sense light or to distinguish between days and nights then this sensor is the cheap and modest solution for you.
