What does an eclipse occur?

An eclipse occurs when the shadow of one celestial object falls on another. This phenomenon can happen in various types of eclipses, such as solar and lunar eclipses. In a solar eclipse, the Moon moves between the Earth and the Sun, casting a shadow on the Earth and blocking out the Sun's light for a short time. Conversely, in a lunar eclipse, the Earth positions itself between the Sun and the Moon, leading to Earth's shadow falling on the Moon.

This understanding highlights the importance of the relationship between celestial bodies and their positions relative to one another. The other options focus on specific phases or positions of the Moon but do not capture the essence of what defines an eclipse, which is fundamentally the interplay of shadows among these celestial bodies. For example, while a full moon is typically associated with lunar eclipses, an eclipse occurs only when the geometry aligns to create a shadow effect. Similarly, a new moon phase is related to solar eclipses but again does not define the general occurrence of eclipses, which is broader and encompasses both types.