Without being able to see the lines, I'm going to guess it's the Equator.
On the globe they are called lines of LATITUDE and are parallel to the equator.
because they are parallel to the plane of the horizon
utx
Only 1: it's horizontal, along the middle.
gradient
horizontal lines represent latitude and vertical lines represent longitude
a table formatted with horizontal lines is called
The horizontal lines are called latitudes and the vertical lines are called longitudes.
On the globe they are called lines of LATITUDE and are parallel to the equator.
When they go from the top, then down.
because they are parallel to the plane of the horizon
The horizontal lines are called latitudes and the vertical lines are called longitudes.
Latitude
The horizontal lines on a network diagram are called rows, and they represent the different entities or components in the network. The vertical lines are called columns, and they show the relationships or connections between the entities.
utx
The Japanese flag has four lines of symmetry. Two of them are a horizontal line halfway up the flag, and a vertical one halfway across the width. It also has two rotation lines of symmetry across the diagonals.
Only 1: it's horizontal, along the middle.