What does this actually mean?

[Splatify]

Hi all I have been messing around with QT for some time now, but every single time I copy this line out when creating my dialogs and I actually have no idea what it means...

Therefore, What does this mean?

OpenDialog::OpenDialog(QWidget *parent) :
        QDialog(parent),
        ui(new Ui::OpenDialog)

OpenDialog::OpenDialog(QWidget *parent) :
        QDialog(parent),
        ui(new Ui::OpenDialog)

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Ok so first off we are using the OpenDialog Constructor. We're pointing to the parent (what exactly is parent) which is of type QWidget. I think that's right. Ok next up we are inheriting the QDialog class (not to sure what the parent bit means) and then I get confused by the part at the end?

Could someone please explain each part to me... I played around with Qt for a while not, but I think it's time I actually started to learn how it works

Thanks for your time and trouble.