Explain the basics of all functions in the code

#include 2 unsigned long ms_runtime; 3 int one ms timer 5 /DEFINE ALL TIMERS AS UNSIGNED LONG 6 IThese timers are incremented every 10ms-0.1s 7 unsigned long timerl; //variable used for blinking LED 8 unsigned long debug_tmr - 30; 9unsigned long button_dbnc_tmr - 0 10 const int buttonPin=2; //button_dbnc_ tmr for debouncing input onst int LED1 = 13; 12 int mem0 13 int val 15 /GLOBAL VARIABLE 16 int state //possible values 0-1> 2 -> 3 - 0 17 void setup () 18 19 read_memory) 20 21 pinMode (LEDI, OUTPUT) Serial.begin(9600) 23 24 void loop () 25 26 27 28 static bool allow_change: static int counter; timers 31 32 if (debug_tmr > 20) Serial.print ("Input "); Serial.println (digitalRead (buttonPin)) debug-tir 0; 36 38