If A and B are two non-empty sets then the set of all possible ordered pairs (x, y) such that the first component x is an element of A and the second component y is an element of B is called the Cartesian Product of set A and B. It is denoted by A × B which is read as “A cross B”.

In the set-builder form, we can write
A × B = {(a, b): a ∈ A, b ∈ B}