Whats A Difference Between Stages In Turbochargers

[hondacivicnos]

Yo guys I dont know what I am even talking about, I played this game 2 days ago.
U can download it from Nittoracing.com (its just a regular racing game but u can upgrade alot of stuff). So I went to the upgrade and there were like 7 turbocharges and they all had diff. stages.
so what is the stages? is it just a game or is it for real cars too?

 

[posol]

stage = company's marketing.... just like a stage 4 clutch. its how the company lists them.

however, there are STAGE compresor wheels.
read this: http://www.honda-tech.com/zerothread?id=523242