The intersection is represented by "∩", and the intersection is the same part of them, such as: A = {1, 2,3,4} and B = {3,4,5,6}, then the intersection of AB is A ∩ B = {3 3,4}.

Union is represented by "∨", and union is all elements of both. Such as the union of AB.

That is, a ∪ b = {1, 2, 3, 4, 5, 6} Note that there cannot be duplicate elements in the set.