Spelling alphabets are also know as radio alphabets, telephone alphabets, or phonetic alphabets. As I understand it, spelling alphabets are examples of acrophony. The words represent letters in oral communications.

The NATO phonetic alphabet is one such spelling alphabet, the US phonetic alphabet is another.

If I want you to understand a series of letters and/or numbers with complete certainty, I might spell it out using the US spelling alphabet. "skybox" becomes "sugar king yoke baker oboe x-ray". Or using the NATO spelling alphabet it's "sierra kilo yankee bravo oscar x-ray"

NATO phonetic alphabet

Alfa, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lama, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu

U.S. phonetic alphabet

Able, Baker, Charlie, Dog, Easy, Fox, George, How, Item, Jig, King, Love, Mike, Nan, Oboe, Peter, Queen, Roger, Sugar, Tare, Uncle, Victor, William, X-ray, Yoke, Zebra

Navajo Code Talkers

The Navajo code talkers in World War II worked out of the Third, Fourth, and Fifth Divisions of the U.S. Marines. They had their own spelling alphabet, reflecting their culture and heritage. They must not enjoy X's in their life.

Ant, Bear, Cat, Deer, Elk, Fox, Goat, Horse, Ice, Jackass, Kid, Lamb, Mouse, Nut, Owl, Pig, Quiver, Rabbit, Sheep, Turkey, Ute, Victor, Weasel, Cross, Yucca, Zinc