Ecliptic Coordinate System

The Ecliptic Coordinate System uses the Sun’s Path around the sky, the Ecliptic, to map the stars.
Whereas the Equatorial Coordinate System maps star positions using the Celestial Equator.

The Ecliptic is the path of the Sun in the Sky, a line along which the Sun always travels during the Year.
The Moon and the visible Planets nearly all follow a line close to the Ecliptic.

The Star positions in the Night Sky were mapped by Hipparchus according to their position relative to the Sun’s Path in the Sky, the Ecliptic, and not the Celestial Equator.
The Ecliptic divides the Earth’s Sphere into two Hemispheres, as does the Equator.
The reason for using the Ecliptic Coordinate System was that most of the orbits of the Planets have a small inclination relative to the Ecliptic, and relative to each other.
Hipparchus did use Right Ascension, and the Equatorial Coordinate System, but only for a few stars.

The Celestial Equator is a Great Circle or disc that divides the Earth’s Sphere into exactly two Hemispheres.
It is on precisely the same plane as the Equator.