Pwm 100 Hz in loop automatic?

I created with Arduino Mega PWM 100Hz, now I wonder how can I make sure to vary the duty on automatic serial monitor.
The code that I created is as follows

 int outputPsuB = 45;  // Timer5-B
//int outputPsuC = 44;  // Timer5-C

void setup()
{

 pinMode(outputPsuB, OUTPUT);  // select Pin as ch-B
 //pinMode(outputPsuC, OUTPUT);  // select Pin as ch-C
 
 TCCR5A = B00100011; // Phase and frequency correct PWM change at OCRA
 TCCR5B = B11010;  // prescaler
 OCR5A = 20000; // 100Hz  se fosse  OCR5A = 10000 verrebbe 200hz
 OCR5B =2000; // 10%
 //OCR5C = 100; // 1%
 }

 void loop(){}

What does this

automatic serial monitor

mean?