just use the search button at the top of the page. search "xcal" or "sct" or just "tune" and you'll get all the details.
it makes your car shift better, and adds a small amount of power, of which you'll be hard pressed to feel. you can also use it as a code scanner. guys with power adders like it because it has some useful end user adjustments, and can be used to data log via obd.