The notation "(1, x), (1, y), (2, x), (2, y)" represents a set of ordered pairs, where each pair consists of two elements. The first element in each pair is a number, either 1 or 2, while the second element can be either x or y. This structure is often used in mathematics to illustrate relationships between different variables. In this case, the pairs can be interpreted as points in a two-dimensional space, where the first number indicates the position along the horizontal axis and the second letter represents a value along the vertical axis. Thus, the pairs can be visualized as points: (1, x), (1, y), (2, x), and (2, y).