Difference between AccuracyGoal and PrecisionGoal

What i开发者_开发知识库s the difference between AccuracyGoal and PrecisionGoal for NIntegrate function?

---

I think this sentence from the Mma help system is almost enough:

With PrecisionGoal->p and AccuracyGoal->a, Mathematica attempts to make the numerical error in a result of size x be less than (10^-a)+Abs[x] 10^-p.