UNION docs

I't unnI don't understand this:
   The UNION operator specifies a table derived from a Cartesian product.   The two tables that represent the direct
operandsof the UNION must   have the same number of columns, and corresponding columns must be   of compatible data
types.</para>  
 
Why do you call it a cartesian product.  I thought a cartesian product
was tableA x tableB, while UNION is really tableA + tableB, right?

If I am right, can you change the docs?  I will leave it as is.  Thanks.

--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026