The waxing gibbous moon happens when the moon is between a 45 and 90 degree angle with respect to the Earth and Sun. So we are seeing more than half of the moon illuminated and less than half in shadow. The word gibbous refers to phases where the moon is more than half illuminated. “Waxing” essentially means growing or increasing in illumination. Each evening, as the moon’s orbital motion carries it towards the Earth-sun line, we see more of the moon’s day side.

Waxing Gibbous Moon