A template is used to output a module, content element, form, or other component. used. In the navigation-area “Layout” under “Templates” the files can be created, stored in folders and edited. These customizations are update-safe.
Template changes are not necessary if you only need an additional CSS ID or CSS class. For most Contao components, you can enter them in the “Expert settings” section. The corresponding names will be taken over by the templates and displayed in the source code.