What are the page headers for secondary lists?

On secondary lists, the system does not display a standard page header and it does not
trigger the event TOP-OF-PAGE.To create page headers for secondary list, you must
enhance TOP-OF-PAGE:

Syntax TOP-OF-PAGE DURING LINE-SELECTION. The system triggers this event for
each secondary list. If you want to create different page headers for different list levels,
you must program the processing block of this event accordingly, for example by using
system fields such as SY-LSIND or SY-PFKEY in control statements (IF, CASE).