Lattitude & longitude marked in map and how it used?

Question

Lattitude & longitude marked in map and how it used?

In: 6

Answer 1

take a flat piece of paper and draw a grid of horizontal and vertical lines on it. The horizontal centerline is your equator. Number the lines above it in escalating sequence, and the lines below it in escalating sequence. The lines above the equator are North, and those below it South. Do the same for the vertical centerline which will now serve as your meridian. To the left is West and to the right is East.

This is the basics of the system, a graph on a map.
The earth is not flat though, sorry it just isnt
So transfer this concept to a sphere.