Simple Arduino code to control servo motors

Question

I am a newbie in Arduino. Right now, I am trying to control a servo motor with an Arduino and I saw an instruction online like this:

#include                //Servo library
    
Servo servo_test;       //initialize a servo object for the connected servo  
int angle = 0;    
     
void setup() 
{ 
  servo_test.attach(9); // attach the signal pin of servo to pin9 of arduino
} 
      
void loop() 
{ 
  for (angle = 0; angle < 180; angle += 1)   
  {                                  
    servo_test.write(angle);                 
    delay(15);                       
  } 
     
  delay(1000);
      
  for (angle = 180; angle>=1; angle-=5)     
  {                                
    servo_test.write(angle);              
    delay(5);                       
  } 
    
  delay(1000);
}

I understand every part of this code, except two lines, which are delay(15) and delay(5). I don't know what the functions of these two lines are. And why 5 and 15 but not both 5 or both 15?

Answer 1

delay() functions help to waits for the servo to reach the position.