Between 1999 and 2001 there were three grades:
IS200 S
IS200 SE
IS200 Sport
With the facelift in September 2001 the grades were renamed:
IS200
IS200 SE
IS200 Sport
The S, compared to the SE, doesn't have a sunroof, leather, heated front seats (not really needed with cloth), headlamp washers, electric drivers seat and front windscreen de-icer. The S also only has a 6 speaker audio system, without a separate amp, and 16" wheels rather than 17" which are on the other grades.