Here's a breakdown:

* Earth's orbit: Earth orbits the Sun in a plane called the ecliptic.

* Moon's orbit: The Moon orbits Earth, but its orbit is tilted at a slight angle to the ecliptic.

* Alignment: For an eclipse to happen, the Sun, Earth, and Moon need to be perfectly aligned. Since the Moon's orbit is tilted, it usually passes above or below the ecliptic plane during its orbit around Earth, meaning it doesn't cross the Sun's path.

Think of it like this: imagine two plates tilted slightly. If you try to stack them perfectly, they won't align easily. Similarly, the Moon's orbit is like the tilted plate, and it only aligns with the Sun's path (ecliptic plane) during specific times, resulting in eclipses.

When eclipses DO happen:

Eclipses occur when the Moon's orbit intersects the ecliptic plane, causing the alignment needed for the eclipse. This happens twice a year, at points called nodes.

Types of eclipses:

* Solar eclipse: The Moon passes between the Sun and Earth, blocking the Sun's light.

* Lunar eclipse: The Earth passes between the Sun and Moon, casting a shadow on the Moon.

Why not every month?

Even though the Moon's orbit intersects the ecliptic twice a year, eclipses don't happen every month because the Moon's orbit is slightly tilted. This means it's not always in the right position during its monthly cycle to cause an eclipse.