What are parallels and meridians what do they serve?

A parallel is an imaginary line on the surface of a planet that runs parallel to the equator. It serves to display the coordinates of an object located on the surface of the planet from north to south.
Therefore, all points that are parallel have the same latitude.
The meridian is an imaginary line that divides the surface of planet Earth from West to East.
Thus, this line is a cross-section of the surface, which is parallel to the axis of symmetry of the planet.
Serves as well as parallels to display the coordinates of an object, but only in this case, all objects that are located on it have the same longitude and different latitude.