#TodayILearned that:

Initialisms are made from the first letter (or letters) of a string of words, but can’t be pronounced as words themselves (e.g. FBI, CIA). Acronyms are made from the first letter (or letters) of a string of words but are pronounced as if they were words themselves (e.g. NASA, hazmat). What I Learned: The Phoenix Project Audiobook - IT Revolution

Personally, I’m not sure that this is a very useful distinction, but it’s interesting

I guess ‘SQL’ is an initialism to those who pronounce it ‘S.Q.L’ and and acronym for those who say ‘sequel’.