Event Block starts a script at the occurrence of an event. The widget event gets captured by the Event block. E.g. Button gets pressed, Text changes in the Text Field, etc.
Event Block has the shape of a Hat Block. Anyone block can get attached to the event block.
To configure a widget Event capture, click on the question mark and then select the widget from the right-hand side widget tree or canvas.
Choose the event from the dropdown menu. It completes the configuration of an Event.