When a component is not properly defined or if the link to the next component does not exist yet, a red checked circle or a warning sign is docked at the component icon.
Mouse over the component, to display the tooltip messages or warnings along with the label. This context-sensitive help informs you about any missing data or component status.
When the tooltip messages of a component indicate that a module is required, you must install this module for this component using the Module view. This view is hidden by default. For further information about how to install external modules using this view, see the Talend Installation Guide.