Lexus means luxury. Every series represents different classes :-
RS is good for Speed and comfort
GS is good for speed and comfort plus expensive
ES The best Series in LEXUS Because of its COMFORT , ECONOMY , And CHEAP ( not that much )
RX Cheap SUV with great COMFORT
LX EXPENSIVE , HEAVY , LUXURIOUS , SUPER COMFORT .
LS cheap and great but not economic.
Lexus is powered by TOYOTA and the reason it got a separate name is because of luxurious. ES series delivers great mileage and its super economic. Some companies uses it from Taxi purpose because of its economic reasons.