Final answer:
A solar eclipse occurs when the Moon moves between the Sun and Earth and casts its shadow on a part of Earth's surface. It can only occur during a new moon phase when the Moon is somewhat nearer than its average distance to Earth.
Step-by-step explanation:
A solar eclipse occurs when the Moon moves between the Sun and Earth and casts its shadow on a part of Earth's surface. If the eclipse is total, the light from the Sun is completely blocked. Solar eclipses can only occur during a new moon phase when the Moon is somewhat nearer than its average distance to Earth.