:m(m)

[enemy]

Please, what means THIS and where does it belong to?

  :m(m)

Many thanks!!!

[MikeyBoy]

It looks like part of an initialisation list. Have a look at:

http://www.cprogramming.com/tutorial/initialization-lists-c++.html

[enemy]

Thanks, Mikey!
It SHOULD be a part of constructor of a class...but I did not get the right point still...

[Cubbi]

For example,

#include <iostream>
struct S {
    int m;
    S(int m) : m(m) {}
};

int main()
{
    S s = 123;
    std::cout << s.m << '\n';
}

[Peter87]

The first m is refers to the member variable. The second m refers to the constructor parameter.