Question

what do you mean by Earth's grid

Answer 1

Grid System of the Earth. meridians and parallels on geographic maps and globes serving to mark off the geographic coordinates of points on the earth's surface—the latitudes and longitudes. All points on a given meridian have one and the same longitude and all points on a parallel, the same latitude.

Answer 2

collective term for the parallel and meridian that from an imaginary grid over the earth surface making it possible to locate a specific point.