If you are talking about KPIs = Key Performance Indicator and asking how that relates to SEO, I would have to say it depends entirely on what you are trying to achieve (pretty much what PinkBitz already said).
In working with SEO clients, the general KPIs are:
- increase in site unique visits
- increase in conversions
- increase in pages/visit and average time on site
- increase in goal conversions
- increase in keywords being ranked for
- increase in site awareness and branding
- increase in SERP positions (because most clients like to think they are "number 1" for something.....even if it doesn't mean increasing their bottom line...go figure)
Hope that helps.