What are eclipes?

Answer 1

Eclipses are shadows.

A lunar eclipse is the shadow of the Earth on the Moon. A solar eclipse is when the Moon's shadow is on the Earth.

Because the Earth is both spinning on its axis and orbiting the Sun, and because the Moon orbits the Earth at a bit of an angle to the ecliptic (the plane of the Earth's orbit) we only get eclipses when the Sun, the Earth and the Moon line up in a straight line. This happens about twice a year.