A(1, 3) refers to a specific point in a two-dimensional coordinate system, where the first number represents the x-coordinate and the second number represents the y-coordinate. In this case, the point is located at 1 unit along the x-axis and 3 units along the y-axis. This notation is commonly used in mathematics and geometry to identify locations on a graph. In a Cartesian plane, the point A(1, 3) can be visualized as a dot positioned in the first quadrant, where both coordinates are positive. This system is essential for various applications, including graphing functions and solving equations in algebra and calculus.