Don't understand : in special members

[Fajsdie]

I am doing the beginners tutorial and I have never seen the : operator after a constructor. Can someone explain to me what Example2 (int initial_value) : total(initial_value) means?

  class Example2 {
  public:
    int total;
    Example2 (int initial_value) : total(initial_value) { };
    void accumulate (int x) { total += x; };
};

[Chervil]

http://stackoverflow.com/questions/1711990/what-is-this-weird-colon-member-syntax-in-the-constructor

[Fajsdie]

thank you,
I haven't found this on stackoverflow