What does it mean if the moon is waxing and waning

Both verbs come from Olde English. 
That's why everybody clearly understood their meaning until
a hundred years ago, but nobody understands them now.

"Waxing"  =  growing

For two weeks after the New Moon, it's growing toward Full.
First it's a waxing crescent for a week, then it's waxing gibbous.

"Waning"  =  shrinking

For two weeks after the Full Moon, it's shrinking toward New.
First it's waning gibbous for a week, then it's a waning crescent.