The line your referring to is the Equator.
the equator is the imaginary line around the earth.
The equator is an imaginary line which indicates where the middle of the earth is and it goes around.
prime meridian
The imaginary line that circles the middle of the earth is called the equator.
Equator...
Equator
Equator
The horizontal line that goes around the "waist" of the Earth is the Equator. The vertical line that goes vertically around the Earth, through the poles, is the Prime Meridian.
the equator
The imaginary line in the middle of the sky is called the Celestial Equator. It is basically just like the equator that goes around the earth. It is basically the dividing line of two halves of the earth.
All lines of Latitude circle the earth, they are imaginary devices used on maps. Latitude is horizontal, think of the Horizon.
The imaginary line between the poles of the Earth around which the Earth spins is called the "axis of rotation".