TButton creates a click button on a Web page. The button's caption is specified by Text property. A button is used to submit data to a page. TButton raises two server-side events, OnClick and OnCommand, when it is clicked on the client-side. The difference between OnClick and OnCommand events is that the latter event is bubbled up to the button's ancestor controls. An OnCommand event handler can use CommandName and CommandParameter associated with the event to perform specific actions.
Clicking on button can trigger form validation, if CausesValidation is true. And the validation may be restricted within a certain group of validator controls according to ValidationGroup.
TODO: custom attributes