what is the top menu on avada theme ?where is it display ?

hello expert ,
i already know what is the main menu ,but what is the top menu ? and where it should be display ? and why when i go to the "theme options>>>menu>>>secondery top menu it says “Secondary Top Menu Options are only available when using Header Layouts #2-5. Your current Header Layout does not utilize the secondary top menu.”

and does the secodery menu=top menu ?

be gratfull for your help