Brett Kelly on acronyms vs. initialisms:
An incredibly common mistake is to refer to the following abbreviations as acronymns: FBI (Federal Bureau of Investigation), FTP (File Transfer Protocol) or CIA (Central Intelligence Agency).
These are not acronyms. They’re called initialisms.
I am sure someone told me this once, but I never remember. I actually thought what are initialisms were actually called “abbreviations”, but apparently, according to Kelly, abbreviation is a more general classification that encompasses both initialisms and acronyms.