How is the ecliptic technically defined in terms of Earth's motion around the Sun?

The plane of Earth's orbit around the Sun

The ecliptic serves as the primary reference plane for mapping the solar system's geometry. Specifically, it is defined as the exact plane that encompasses Earth's entire journey as it revolves around the Sun over the course of one year. This definition is critical because the solar system originated from a vast, rotating disc of gaseous material and dust; consequently, the subsequent gravitational collapse and formation of the major planets resulted in nearly all of them maintaining orbits situated very closely to this initial plane. As viewed from Earth, the Sun appears to traverse this specific path across the celestial sphere throughout the year, reinforcing its role as the baseline for astronomical measurement.