C++ : What is done in the following example? Is it multiple Inheritance? [duplicate]

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• What is this weird colon-member (“ : ”) syntax in the constructor? 12 answers

MainWindow::MainWindow(const char* f, QWidget* p) : QMainWindow(p), m_database() {
    // ................
}

Why is m_database used before the curly brackets? It can't be multiple Inheritance since m_database is not a class?

It is declared in the .h file like this.

private:
    BRLCAD::ConstDatabase m_database;