Playing games with Calibration sketch

Below is the code to an Arduino sketch, Calibration. I'd use this to calibrate the sensitivity of the input sensors and perhaps the output signal to another piece. My questions are in BLUE.


Calibration

Demonstrates one technique for calibrating sensor input.  The
sensor readings during the first five seconds of the sketch
execution define the minimum and maximum of expected values
attached to the sensor pin.

The sensor minimum and maximum initial values may seem backwards.
Initially, you set the minimum high and listen for anything 
lower, saving it as the new minimum. Likewise, you set the
maximum low and listen for anything higher as the new maximum.

The circuit:
* Analog sensor (potentiometer will do) attached to analog input 0
* LED attached from digital pin 9 to ground

created 29 Oct 2008
By David A Mellis
Modified 4 Sep 2010
By Tom Igoe

http://arduino.cc/en/Tutorial/Calibration

This example code is in the public domain.

*/


// These constants won't change:
const int sensorPin = A0;    // pin that the sensor is attached to
const int ledPin = 9;        // pin that the LED is attached to
                                     // THE LED WOULD IN TURN LEAD TO THE 
                                        PLAYBACK CHIP

// variables:
int sensorValue = 0;           // the sensor value
int sensorMin = 1023;        // minimum sensor value
                                              //  HOW IS THIS VALUE ARRIVED TO?
int sensorMax = 0;           // maximum sensor value
                                    



void setup() {
 // turn on LED to signal the start of the calibration period:
 pinMode(13, OUTPUT);
 digitalWrite(13, HIGH);


 // calibrate during the first five seconds 
 // DOES THIS MEAN THAT I ONLY HAVE 5 SECONDS TO CALIBRATE THIS? while (millis() < 5000) {
   sensorValue = analogRead(sensorPin);


   // record the maximum sensor value
   // HOW IS THIS DONE?   if (sensorValue > sensorMax) {
     sensorMax = sensorValue;
   }


   // record the minimum sensor value
   // HOW IS THIS DONE?   if (sensorValue < sensorMin) {
     sensorMin = sensorValue;
   }
 }


 // signal the end of the calibration period
 digitalWrite(13, LOW);
}


void loop() {
 // read the sensor:
 sensorValue = analogRead(sensorPin);


 // apply the calibration to the sensor reading
 sensorValue = map(sensorValue, sensorMin, sensorMax, 0, 255);


 // in case the sensor value is outside the range seen during calibration
 sensorValue = constrain(sensorValue, 0, 255);


 // fade the LED using the calibrated value:
 analogWrite(ledPin, sensorValue);
}