int pot=A0;  //Analog 0 pin named as sensor
int  led=11;   //Pin-11 is declared as output led

void setup()                                                          
{
pinMode(led, OUTPUT); //Pin-11 is declared as output 
//We dont need to declare the A0 pin as input since it is predefined as input                                                
}

void loop()
{ 
int reading=analogRead(pot); //Reading the voltage out by potentiometer
int bright=reading/4;           //Dividing reading by 4 to bring it in range of 0 - 255  since 1042 form pot need to by 256 for led to work                             
delay(10);                     //Delay is not necessary you can remove it
analogWrite(pot, bright);    //Finally outputting the read value on pin-9 fading led
}