what are preprocessor directives in c++ code example

Example: c++ what is #define

// #define is a macro that lets you use an alias name to
// make code more readable. During C++'s preproccessing stage, your macro
// will be replaced with the suitable code needed for proper compiling. 

#include <iostream>
// used to define constants, types, functions and more....

#define SIZE 5 
#define MacroInt int 
#define getmax(a,b) ((a)>(b)?(a):(b))

int main(){
  	MacroInt myIntAsMacro = 7;
    std::cout<< getmax(SIZE, myIntAsMacro); // will return 7
}