The set containing all objects that are a member of A, B, or both is the union of the sets A and B, represented as A B. The set 1, 2, 3, 4 is made up of the union of the numbers 1, 2, 3 and 2, 3. The set containing all objects that are members of both sets A and B is the intersection of the sets A and B, indicated by the symbol A B.