Why we are using * character when we are creating button but we aren't adding it to app instance?

#include <QApplication>
#include <QPushButton>

int main(int argc,char *argv[])
{
    QApplication app(argc,argv);
    QPushButton *button = new QPushButton("Button Text");
    QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit()));
    button->show();
    return app.exec();
}

When should we use * and & and . and -> ?