Pagebreak button in DJ-Catalog2 is managed by DJ Catalog2 - Pagebreak plugin. It allows to separate from the content (text above first pagebreak), named sections which will be displayed in divs, tabs or accordion (depending on the plugin settings).

To set effect type, navigate Extensions > Plugin Manager and choose Dj-Catalog2 - Pagebreak

See an example without effect:

See an example with accordion effect (content dynamically appears/disappears after clicking on pagebreak title):

See an example with tabs effect:

You can use pagebreak by pressing Pagebreak button in detail view of producer, category or product:

Then you will see a page where you have to choose a title:

Press Insert Pagebreak and that's it.