Pretty much as Horatio said before.
Authentique and Expression are "base" models of sport/elegance range.
Dynamique/Privilege are mid range & Gt/Initiale are top of the range.There are overlaps.
The Dynamique/Privilege being most "Popular" derivatives. For an older (2004) spec Lag the Dynamique willhave 17" alloys,sports seats and rear spolier, whereas the Privilege will have auto lights,6 discd cd changer/upgrade stereo, "driver information display" as appossed to normal warning lights,instead of large alloys,spoilers etc.
There are also some subtle differences between hatchback and sporttourer ( or there was - not sure about current facelifted ones).
Dynamique sport tourer will have xenon lights as std,hatchback wont.
Privilege sporttourer has rear parking sensors as std,hatch doesn't.
Confused ????? - I am