FTP is a set of rules that computers follow when they send files from one machine to another over a network. People almost always say the three letters, F-T-P, not a spoken word, and they write it in capitals. It is a work word from the early internet: people who look after servers and websites still use it, but it is not a home word. You may also hear it as a verb in tech talk — “I’ll FTP those files to you” — meaning send them that way. Though actually, most of us now move files with a cloud folder, email, or a normal web page, so a learner will meet FTP more often in old instructions than in daily chat. It is not secret or rude; it is just old specialist kit.