arduino pwm

int pwm1 = 3 ;
int pwm2 = 5 ;
int led = 13 ;

void setup()  { 
  // nothing happens in setup
  pinMode(pwm2,OUTPUT) ;
  digitalWrite(pwm2,LOW) ;
} 

void loop()  { 
  // fade in from min to max in increments of 5 points:
  for(int fadeValue = 0 ; fadeValue <= 255; fadeValue +=5) { 
    // sets the value (range from 0 to 255):
    analogWrite(pwm1, fadeValue);
    analogWrite(led, fadeValue) ;   
    // wait for 30 milliseconds to see the dimming effect    
    delay(100);                            
  } 

  // fade out from max to min in increments of 5 points:
  for(int fadeValue = 255 ; fadeValue >= 0; fadeValue -=5) { 
    // sets the value (range from 0 to 255):
    analogWrite(pwm1, fadeValue);
    analogWrite(led, fadeValue) ;    
    // wait for 30 milliseconds to see the dimming effect    
    delay(100);                            
  } 
}