Waxing – when the illuminated portion of the moon is increasing, or “growing”..
Waning - when the illuminated portion of the moon is decreasing, or “shrinking”.
Crescent - when the moon is less than halfway illuminated.
Gibbous - when the moon is more than halfway illuminated.
New Moon: The illuminated half of the Moon faces directly toward the Sun, and the dark or unilluminated portion of the Moon faces directly toward Earth, so that the Moon is invisible as seen from Earth (except during a solar eclipse).
Waxing Crescent: The illuminated “crescent” of the moon’s disk is increasing. The right side of is 1-49% visible.
First Quarter Moon (FQ): The illuminated section of the moon's disk is increasing. The right side is 50% visible.
Waxing Gibbous: The illuminated, “pregnant” section of the moon's disk is increasing. The right side is 51-99% visible.
Full Moon: The moon's illuminated side is facing the Earth, and is fully visible.
Waning Gibbous: The illuminated section of the moon’s disk is decreasing. The left side is 51-99% visible.
Waning Crescent: The illuminated section of the moon's disk is decreasing. The left side is 1-49% visible.
Moon phase image courtesy of wikipedia.com.