Jake wrote:
"Venn diagrams or set diagrams are diagrams that show all
hypothetically possible logical relations between a finite collection
of sets (aggregation of things). Venn diagrams were conceived around
1880 by John Venn. They are used to teach elementary set theory, as
well as illustrate simple set relationships in probability, logic,
statistics, linguistics and computer science (see logical
connectives)."

I think that explains things perfectly and simply and should serve to
end all further argument.

(I think Vicky was being tongue in cheek when she posted).

:-)

I will now wait for someone to explain the explanation to me (and no
doubt someone else will be able to explain the explanation of the
explanation).

It's one of those diagrams that looks like someone has put a bunch of coffee
mugs down on a sheet of paper, and all the people go in the circles. So the
coffee stain is 'people who are posh' and the tea stain is 'people who own
chickens' and the bit where the tea and coffee stains overlap is the posh
people who own chickens. And people outside both drink stains are people
who aren't posh and don't have chickens.
Then you can put a beer bottle down to make another circle that is 'people
who microwave their pork pies' and it can overlap the other 2 circles, and
you need to move all the people to their correct position again.

It's the sort of thing you do at school cos it's sort of fun, but if you
need to use it outside of school you're probably in the wrong job!