Hi
 
int val = 7;            //  can changes as the integer val is used
 
const int val2 = 9; // never changes as the integer val2 is used, so val2 will always remind 9

Hi Alberto.

I think it is worth taking a look at this discussion: https://forum.arduino.cc/index.php?topic=115386.0#targetText=The%20difference%20between%20int%20and,it%20must%20not%20be%20const.

It explains the difference between int, const int, and #define.

I hope this helps.

Regards,

Sara