The axes divide the plane into four quadrants. Quadrant I has positive x and positive y. Quadrant II has negative x and positive y. Quadrant III has negative x and negative y. Quadrant IV has positive x and negative y.
Knowing the quadrant helps you catch sign errors. If a point should be in Quadrant III but your calculation puts it in Quadrant I, you know something went wrong.
Many geometry problems span multiple quadrants. The formulas work the same in all four regions.