Here is the sample code:

class Human
{
    private:
        int age;
        std::string name;
    public:
        Human(std::string humansName = "Adam", int humansAge = 25):name(humansName), age(humansAge) {
            std::cout << "Constructed a human called " << name;
            std::cout << ", " << age << " years old" << std::endl;
        }
};

versus this:

class Human
{
    private:
        int age;
        std::string name;
    public:
        Human(std::string humansName = "Adam", int humansAge = 25) {
            age = humansAge;
            name = humansName;
            std::cout << "Constructed a human called " << name;
            std::cout << ", " << age << " years old" << std::endl;
        }
};

Why does the constructors with initialization lists exist? What are the use cases? Why should it be preferred? Thank you for your responses.