VoIP is a way of making phone calls over the Internet instead of over the old telephone lines. The letters stand for "Voice over Internet Protocol" — your voice is turned into computer data, sent through your Internet connection, and turned back into sound at the other end. Because the call travels the same road as your email and your videos, it usually costs much less than a normal long-distance call, and sometimes nothing at all. Skype, LINE calls, WhatsApp calls, Google Meet, and the phone system in most modern offices all run on VoIP. In everyday talk almost nobody says the word — people just say "call me on LINE" or "internet call". You will meet VoIP mostly in three places: computer or telecom company writing, job descriptions for IT people, and the settings menu of an office phone. It is a technical, work-flavoured word, not a chatty one. It works as a noun on its own ("We switched to VoIP last year") and very often sits in front of another noun ("a VoIP phone", "a VoIP provider", "VoIP calls"). Note that it names the technology, not one single company's app — LINE uses VoIP, but LINE is not "a VoIP". Say it as "voyp" (one syllable, rhyming with "boy" plus p) or spell it out "V-O-I-P"; both are common, and older engineers often prefer the spelled-out version.