This is a variation of disp = posts (List of Posts / Items) where posts are filtered on a selection of multiple categories:
Default Container and Widgets
Below is the default main Container and Widgets of this $disp_detail that comes with b2evolution. Yours may look different depending on the particular skin in use and the widgets currently installed and how they are configured.
Tip: We can fully customize how this disp variation will look by creating or replacing the
_posts.disp.php file in the currently used skin’s folder.