When the Moon is directly opposite the Sun, it's called a Full Moon. Here's what happens:

* The Moon is fully illuminated: Because the Sun is shining directly on the side of the Moon facing Earth, we see the entire lunar disk illuminated.

* Tides are stronger: The Sun and Moon's gravity combine to create stronger than usual tides, leading to higher high tides and lower low tides.

* Lunar eclipses: If the Moon is perfectly aligned with the Earth and Sun, the Earth's shadow can fall on the Moon, causing a total lunar eclipse.

Let me know if you'd like more detail on any of these points!