Reference sections are pre-created sections that are meant to be created once and then mentioned everywhere. They are perfect for regulary returning stuff like call to actions.
You can create a reference in the WordPress admin and going to Section Templates -> Add new. Here you can create a new post with your reference section. This section can be used in two ways:
References have their own default classes, because they don’t really work in the regular Section flow (since they belong to a different post, officially ).
The outlier in this is the template class. Referencese have a different template hierarchy than regular sections.