RE: What is a
Waivers aren't required to fly turbines in the USA. If you fly and are an insurance customer of the AMA company then you need a waiver. The AMA company provides secondary insurance for most flying clubs and model contests in the USA. The AMA wants you to have passed some tests for a "waiver" before they will provide you secondary insurance for your turbine powered aircraft.
The AMA company is not associated with the goverment and regulations of the USA. People often mix up the company with the goverment.