void setup() {
  pinMode(13, OUTPUT);//Initializes pin 13 to be an Output 
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(13, HIGH);//Sets the LED on Pin 13 to HIGH or ON
  delay(250);//Makes the the LED wait for 250 miliseconds 

digitalWrite(13, LOW);//Switches the LED light off
delay(250);//Then waits again for 250 miliseconds 
}