How do you draw venn diagram?

You draw a rectangle for the universe of all things in your set and then you draw circles inside the rectangle for each set. If the sets have a non-zero intersections, than you draw and overlap of the circles to show that. So the venn diagram consists of overlapping circles. The combined area of the circles is the union. By the universe, I mean all possible things that you are dealing with. For example, If you are looking at a school, that would be the universe. Maybe one set is students taking chemistry and one is students taking math. Those are two circles. They probably overlap and the overlap is the intersection. The union is the students taking both. The rectangle represents all students in the school.