There are many versions of platform S60. The oldest is 1st edition (you can read 1st Edition as 1st Version). Every version can have several feature packs (FP). They denote new features added to the specific version.
List of all Editions & Feature packs (the newest is on the top:
S60 3rd Edition, FP 1
S60 3rd Edition
S60 2nd Edition, FP 3
S60 2nd Edition, FP 2
S60 2nd Edition, FP 1
S60 1st Edition, FP 1 (S60 Platform 1.0)