what is c++ function

#include <iostream>

// Function declaration
int addNumbers(int a, int b);

int main() {
    // Function call
    int result = addNumbers(5, 7);

    // Output the result
    std::cout << "Sum: " << result << std::endl;

    return 0;
}

// Function definition
int addNumbers(int a, int b) {
    // Function body
    int sum = a + b;

    // Return statement
    return sum;
}