Coordinate axes are the two perpendicular lines used in a coordinate system to define the position of points in a plane. The horizontal line is called the x-axis, while the vertical line is known as the y-axis. Together, they create a grid that helps in locating points using pairs of numbers, called coordinates. Each point on the grid is represented by an ordered pair, such as (x, y), where x indicates the position along the x-axis and y indicates the position along the y-axis. This system is widely used in mathematics, physics, and engineering to analyze and visualize relationships between different variables.