How will you describe the position of a table lamp on your study table to another person?
To describe exact location of the study lamp, we need to know distance of study lamp from one horizontal edge and one vertical edge.
Let's take an example. Suppose table lamp is placed on the study table ABCD. The point P represents the position of study lamp. The perpendicular distance between study lamp and horizontal edge CD is 10 units. The perpendicular distance between study lamp and vertical edge AD is 15 units. We can say that lamp is placed at the point (15, 10).