Hello keren,
You are correct. When using FAST you will use the "FAST Search Keywords" section which also included visual best bets. The "Search Keywords" section is used by the built-in SharePoint search. And remember, even if you install FAST for SharePoint, the built-in
search is still there if you for some reason decide to use for regular crawls (and it's used for people search via the FAST Query SSA).
Regards,
Mikael Svenson
Search Enthusiast - SharePoint MVP/WCF4/ASP.Net4
http://techmikael.blogspot.com/