Описание тега ctor-initializer
Constructor initializer list. In C++, the initializer list is the place where initialization of the object should occur. Is where the constructors for base classes and members are called. Members are initialized in the same order as they are declared, not as they appear in the initializer list.
Constructor initializer list. The initializer list is the place where initialization of the object should occur. Is where the constructors for base classes and members are called. Members are initialized in the same order as they are declared, not as they appear in the initializer list.
If a parameter in the constructor has the same name as one of the members, the ambiguity of that identifier being passed in a constructor call inside the initializer list is resolved choosing the parameter (and not the member).
Members or base classes not present in the list will be default constructed.
Source: http://en.cppreference.com/w/cpp/language/initializer_list