‘A crescent shape  is a symbol or emblem used to represent the lunar phase in the first quarter (the "sickle moon"), or by extension a symbol representing the Moon itself.

It is used as the astrological symbol for the Moon, and hence as the alchemical symbol for silver. It was also the emblem of Diana/Artemis, and hence represented virginity. In Roman Catholic Marian veneration, it is associated with the Virgin Mary.

Text from Wikipedia