All about Moon Phases
Throughout each month, the Moon appears to change shape while it appears in the sky at different times, including in broad daylight! Anyone can observe these changes as they happen. The Moon’s ever-changing shapes are called “lunar phases.”
The Moon’s shape changes for the following reasons:
The Moon orbits Earth.
Both Earth and the Moon orbit the Sun.
The Moon’s orbit is the same length as the time it spins on its axis (about 28 Earth days), which means that we see the same part of the lunar surface all month.
The Sun illuminates both Earth and the Moon.