In general, the Cartesian product of two sets is a new set defined by
The pair is ordered pair because the order is important, that is to say, in general .
One of the most important Cartesian products in mathematics is which is precisely the Cartesian Plane xy. The set is a subset of which is the set of all the points in the Cartesian plane whose coordinates are integers numbers. So, sketching the set we have a picture as the shown below.