What are the 3 grades of copper pipe used in plumbing?

some countries go by class depending on the thickness of the copper pipe. Class 0 being the thinnest of the classes, which can be used in general plumbing applications right through to Class 3 which is very thick and is used when laying in concrete, or when high water pressures are evident or when pipes have to be layed inside and expensive aritcles cannot be damaged due to burst pipes