The document discusses the Cartesian coordinate system. It explains that the system uses a horizontal and vertical number line that intersect at the origin (0,0) to locate points in space. Any point has coordinates written as an ordered pair (x,y) representing its distance from the x-axis and y-axis. The plane is divided into four quadrants based on whether the x and y values are positive or negative. Examples are given to demonstrate plotting points in the quadrants and identifying the axes.