SI has V-Tec, it is there "sports" model... Other models vary on accessory packages like power windows and mirrors, or sunroofs, or leather, etc. Since you have Internet to post this question, check out Honda's website. (Won Best answer on this site last time it was asked)Wikipedia says:The Honda Civic Si is a sport compact / hot hatch version of the compact car Honda Civic built by the Japanese automaker Honda. The Si designation, which stands for "Sport Injected", was formerly used in both Japan and North America signifying the most powerful Civic available in market. For the Japanese and European markets, however, the Civic Type R has been adopted as the high-performance variant of the Civic, from 1997 (starting with the EK9 hatch) in Japan and from 2001 (starting with the EP3 hatch) in Europe. In Canada, the model known as the Si also included additional features found in the EX and EX-L model in the US market, such as heated side mirrors.