Eclipses of the Sun are caused by the alignment of the Sun, Moon, and Earth. Here's how it works:

* Solar Eclipse: A solar eclipse occurs when the Moon passes between the Sun and Earth, blocking the Sun's light from reaching Earth. This alignment creates a shadow on Earth.

* Lunar Eclipse: A lunar eclipse occurs when the Earth passes between the Sun and Moon, blocking the Sun's light from reaching the Moon. This alignment creates a shadow on the Moon.

Therefore, the motion causing eclipses is the orbital motion of the Moon around the Earth, and the Earth around the Sun. The specific alignment of these bodies in space determines the type of eclipse that occurs.