Elements  -  The members of a set.

Intersection  -  The intersection of two sets, denoted A∩B ("A intersect B") is the set of all members contained in both A and B.

Union  -  The union of two sets, denoted A∪B ("A union B"), is the set of all members contained in either A or B or both.

Venn diagram  -  A representation of two or more sets that shows the relationship between them: