In this circuit the cathode of LED is connected to the ground and it's anode is connected to a 220 ohm resistor. As the excess current can burn out the LED, hence to limit the current through LED we use resistor. Other end of resistor is connected to pin number 2 (Digital input/ output pin) of Arduino.
As the code get's uploaded in the microcontroller, the LED will glow as per the delay written in the void loop()
