Definition - What does Initialism mean?
An initialism is a term for any word composed of the initial letters of other words, in which the word is pronounced by pronouncing each of the individual letters. People think of initialisms as a class of acronyms. The difference is that acronyms are typically pronounced as a single readable or phonetic word.
Techopedia explains Initialism
While the word “initialism” seems to have been coined in the 1950s, it never really caught on in general language. People tend to refer to both acronyms and initialisms as acronyms. However, while a word like random access memory or RAM is an acronym, words like HTML, IBM and PC are all initialisms, because the reader spells out the combination of letters instead of treating it like a single readable word. In many cases, it may be unclear whether an abbreviation is an acronym or an initialism, and different speakers may use either pronunciation. This is particularly true in tech, where less tech-savvy people may tend to spell out an acronym.