Call is used to invoke a web service. With Call you can post parameters to a JSON web service and get the result. Calls supports simple JSON results and also reporting a success or failure condition. You can have many Calls in one page and invoke them from Actions. Actions will invoke Calls in their sorting order one after one. Depending on the action type you can leave the page to a new one and pass the Call result with Action parameters or you can stay on the current page and refresh the view to use the result data.