Calavera is a representation of a human skull. The term is most often applied to decorative skulls used in the Mexican celebration of the Day of the Dead and the Roman Catholic holiday All Souls' Day. Skulls usually represent a departed soul.

These skulls were "for sale" for people to take home and & use on their personal family Día de Muertos altars.
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From the gallery https://pbase.com/britestar/day_of_the_dead_2019