### Theory:

Do you know how the graph came into existence?
 Rene Descartes is a famous French mathematician.  One day Rene became quite ill. While he was taking rest in his bed, he noticed an insect flying around the ceiling and sits at various places on the ceiling. He wanted to know all the places where the insect sits. So, he draw horizontal and vertical lines in the paper which indicates the ceiling.

These points mark the places where the insect sits on the ceiling. He plotted the points using directions and the insect's movement in the north, south, east and west directions. Then, later he called the place as $$(x,y)$$ where $$x$$ indicates the horizontal direction (east and west direction) and $$y$$ indicates the vertical direction (north and south direction). This is how graph came into existence.
Reference:
https://en.wikipedia.org/wiki/Ren%C3%A9_Descartes#/media/File:Frans_Hals_-_Portret_van_Ren%C3%A9_Descartes.jpg
Frans Hals drew the portrait of Rene Descartes.