C++11 - What is the difference between CTOR() = default and empty CTOR(){}?

Question

C++11 introduced new keyword default to force creation of default constructor:

class MyClass {
    MyClass() = default; // <==
    MyClass(int num);
};

I could not find the reason to use it over empty constructor.

class MyClass {
    MyClass() {} // <==
    MyClass(int num);
};

Could anybody enlighten me?

Answer 1

The = default; constructor is trivial, which no user provided constructor ever is - even an empty one.