This applet lets you highlight the set A, the set B, the universal set S, the empty set {}, the complement of A (Ac), the complement of B (Bc), the intersection of A and B (AB), the union of A and B (A or B), the intersection of the complement of A with B (AcB), and the intersection of A with the complement of B (ABc). You can drag the events A and B around, which changes the probability of their intersection and of their union.