Answer 1

After designing it, they write a program to either turn it into the same program in another language (compiler) or to read and execute what the program says line-by-line (interpreter).

Answer 2

for beginner, try this in C++.
#include <iostream>

#define _start int main(){
#define SET uint8_t
#define ADD(a, b) a + b
#define PUT std::cout<<
#define _end retrun 0;}

_start
SET a = 2;
SET b = 4;
SET c = ADD(a, b);
PUT c
_end

Hopefully this works, just did it freestyle