**Definition of Full Moon**

The full moon is a phase of the moon that occurs when the moon is positioned directly opposite the sun as observed from the Earth. During this phase, the entire illuminated side of the moon is visible from our planet, making it appear fully round and bright in the night sky.

**Explanation in Detail:**

**1. Lunar Phases:**
The moon goes through a cycle of eight distinct phases as it orbits around the Earth. These phases are a result of the varying positions of the moon, Earth, and sun. The full moon is one of these phases and is considered the brightest and most easily recognizable.

**2. Positioning of the Moon:**
During a full moon, the moon is located on the opposite side of the Earth from the sun. This means that the sun, Earth, and moon are aligned in a straight line, with the Earth in the middle. As a result, the entire side of the moon that is facing the Earth is fully illuminated by the sun's light.

**3. Appearance in the Sky:**
When the moon is in its full phase, it appears as a complete, round orb in the night sky. Its surface reflects sunlight, creating a bright and luminous appearance. The full moon is visible throughout the night, rising in the east as the sun sets in the west. It reaches its highest point around midnight and sets in the west as the sun rises in the east.

**4. Effects on Earth:**
The full moon has various effects on Earth. It influences the tides, causing higher and lower tides than usual due to the gravitational pull of the moon on Earth's oceans. Additionally, the brightness of the full moon can affect nocturnal animals and their behavior. It also provides ample light for nighttime activities and has cultural significance in many societies.

**Conclusion:**
In summary, the full moon is a phase of the moon where it appears fully illuminated from the Earth's perspective. It occurs when the moon is positioned opposite the sun, resulting in a round and bright appearance in the night sky. The full moon has various effects on Earth and holds cultural significance in many societies.