Cycle
The moon takes a little more than 29 days to go from a new moon to a full moon and back again. All four phases are visible during that cycle.
Crescent Moon
A crescent moon takes place between the new moon and the half moon. It looks like a thin sliver of light, curved into the shape of a crescent.
Half Moon
The half moon looks like a silver dollar sliced in two. One half is filled with light, the other half is dark.
Gibbous Moon
A gibbous moon is more than half full, but has not yet reached full moon status.
Full Moon
A full moon reflects light from every part of its visible surface, looking like a complete circle in the sky.