Cartesian product
From Conservapedia
The Cartesian product of two sets A and B is the set (usually denoted by A × B) consisting of all ordered pairs (a, b) where 
and 
. The Cartesian product is named after René Descartes, who invented this concept.
A common example of a Cartesian product is the coordinate plane, 
. This is all ordered pairs (a,b) of real numbers a and b. It is used for graphing functions on the real numbers.
