This celebration evolved from ancient Aztec festivals that venerated gods like Mictēcacihuātl, the powerful lady of the dead. It has been added to and blended with many other traditions and cultures.
“Dia de los Muertos,” is celebrated across Mexico and beyond with parades, families honor their ancestors by creating altars with their favorite food and drink, lighting candles, playing music, and displaying their images — an invitation to these souls to return and linger briefly among the living. The recent Disney film "CoCo" is a beautiful introduction to this celebration.
It explores the belief that there are three deaths: “first death” is the physical one, the death of the body. The “second death” is the moment the body is laid to rest returned to nature’s cycle. The “third death” the film explores is the most definitive: the moment the last memory of you fades. Día de Muertos helps to delay that final death.
On National Geographic.com site Caitlin Etherton writes "While every place incorporates different traditions (spicy rum in Haiti, baby-shaped bread in Ecuador) all festivities have one thing in common—a joyful and rich celebration of those dearly departed. This is a time for sharing funny stories about those who have passed, for eating and remembering your great great grandma’s favorite soup, for both cleaning the graves and dancing in the streets. Markets across Mexico spill over with sugary candy, copal incense, pricked paper banners, and mountains of bread. Everywhere everything is flooded with marigolds."
"If there is one festival motif it would be calacas and calaveras, skeletons and skulls. Children in skeleton face-paint chew sugary skull candy. Bone-shaped bread and skull maracas balance on tables between stacks of tiny ceramic skulls. Skull-shaped balloons are paraded through town behind costumed skeletons who dance their skeleton marionettes. Even the poems written for the festival are called calaveras, satirical little verses that joke to remind us that everyone, rich or poor, famous or unknown, is headed to the same fate—back to the soil, to bone, to ash."
“Day of the Dead opens up the dimension of being able to communicate with the spirit of not only individuals who have passed away, David Carrasco, Neil L. Rudenstine Professor of the study of Latin America at Harvard Divinity School, “but what I call ‘convivencia,’ which means you’re living together in a family, nurturing each other in a family — even the family that has passed on to the other side.”
The alters, special food, marigold blossoms, known as “flor de muerte” in Spanish, or “flower of the dead,” is said to guide the spirits home. Where their memories are cherished and renewed each year at this time.