How does prouct exports works in admin area

I have created a new module to view the messages sent to the admin.I want to export the messages in the exel and xml sheets.i learnt that when i click on  <button type="submit" name="exportexcel-all"> from export dropdown . The following function is fires .

        [HttpPost, ActionName("List")]
        [FormValueRequired("exportxml-all")]
        public ActionResult ExportXmlAll(OrderListModel model)

so please explain me how does it understand that ExportXmlAll button shoud call when i click on button