What does $A^B$ mean where A and B are complexity classes?
The "Polynomial Hierarchy" page says:
$A^B$ is the set of decision problems solvable by a Turing machine in class A augmented by an oracle for some complete problem in class B
In that case what is a Turing machine in class A?
(besides just a machine of some sort that can solve problems in A, because that doesn't give any insight as to what it means to augment such a machine with an oracle)
The motivation for this question was: What is a Turing Machine in class coNP.