The phonetic language – also known as the ‘spelling alphabet’ or the NATO phonetic alphabet – is used by professional communicators, especially police, military and other emergency and armed forces, to identify letters precisely, either when communicating initials, abbreviations or spellings of words.
It is for speaking over a radio or other electronic communication system. Often people don’t speak clearly so if they said “D” the person on the other end might hear “T”. So you would say “Delta” or “Tango” and the person hearing it would know what you are saying. The phonetic alphabet used for confirming spelling and words is quite different and far more complicated to the phonetic alphabet used to confirm pronunciation and word sounds, used by linguists, speech therapists, and language teachers, etc.
Different variations of the phonetic language exist but the International Radio telephony Spelling Alphabet, commonly known as the ICAO phonetic alphabet, sometimes called the NATO alphabet or spelling alphabet and the ITU radiotelephonic or phonetic alphabet or military alphabet, is the most widely used radio telephonic spelling alphabet.
The 26 code words in the NATO phonetic alphabet are assigned to the 26 letters of the English alphabet in alphabetical order as follows: Alfa, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu.
After the phonetic alphabet was developed by the International Civil Aviation Organization (ICAO) it was adopted by many other international and national organizations, including the North Atlantic Treaty Organization (NATO), the International Telecommunication Union (ITU), the International Maritime Organization (IMO), the American Federal Aviation Administration (FAA), the Alliance for Telecommunications Industry Solutions (ATIS), and the International Amateur Radio Union (IARU).
Source: NATO phonetic alphabet