As the moon moves through its monthly orbit around the earth, its shape appears to change. Due to the shadows caused by the earth, the moon variously appears as a complete sphere, the full moon and crescents. There are eight phases the moon goes through each month. The times between the full moon and the new moon are called waxing and waning. When the moon is in alignment with the sun on the same side of the earth, it is termed "new." This is when it is not visible. Note that a complete lunar eclipse is rare due to the moon's orbit not being completely straight.
Notice if the shadow cast by the Earth is on the left side of the moon. This indicates the moon is waxing crescent. Simply put, this means the moon is coming out of the not-visible new moon state and on its way to a full moon. Waxing means "growing."
Watch to see if the shadow is on the right side of the moon. A right shadow announces the waning of the moon back to the new moon phase after the full moon has occurred. Waning is a term for "shrinking."
Note if the moon is at the quarter mark. This signifies the first or last quarter of the lunar phase. The first quarter is indicated by a shadow on the left side, while the last quarter is on the right. The time after the first quarter is known as "waxing gibbous." After the full moon, the time is then called "waning gibbous." Once the last quarter is observed, the moon then wanes crescent before returning to the new moon phase.