Hello,
it could be either inline widget macros like {^widget|(name)DateTime|(JsUseServerTime)False|(widget_displayname)Date+%26+time^}
-> https://docs.kentico.com/display/K8/Inserting+widgets+using+the+editor
or placeholder macros in hierarchical transformations like {^SubLevelPlaceHolder^}
-> https://docs.kentico.com/display/K8/Using+hierarchical+transformations
Best regards,
Jan Hermann