ISO is nothing more then "SAY WHAT YOU DO, AND DO WHAT YOU SAY YOU'LL DO".

ISO was adopted here in the states for those companies who do business abroad in the UK.
ISO = International Standards Organizion.

It is also a way to CYA, with a paper trail. It does get very detailed at times. You'll only find this at the upper end of the spectrum not at the local level where you're a 1-2 man operation working a service truck. Mostly you're manufacturing companies will have an ISO cert. and as Gloria stated they are audited to make sure they are "DOING WHAT THEY SAID THEY WERE GOING TO DO".