Remember the old phone network? You made a call, owned that connection for as long as you wanted it.
Then this thing called VoIP came along. Promises of free phone calls, and all sorts of enhanced features, and all you needed was a PhD in Network Design to make it work (or maybe not work).
What is VoIP? It stands for Voice over Internet Protocol. So, it just means sending voice across a network that uses the Internet Protocol (the most famous of which is the internet itself), rather than across an old-school telephone circuit.
VoIP traffic has to share the connection between you and the person you are calling with all the other traffic on the network. Videos, pictures, emails, web page traffic; it’s all happening on the same network. If the network is working well, everything gets to where it’s going and all is well.
Unfortunately, if something doesn’t get where it’s going, the human ear can’t handle that. If even part of a word is lost, it becomes almost impossible to carry on a conversation. Computers don’t care; they’ll just retransmit. Humans are more fussy. We don’t like having to ask somebody to repeat what they said.
So, yes, VoIP is a bit more complex. Instead of a dedicated connection across the circuit-switched telecom network, there is a stream of tiny little packages, each one containing just a small part of the conversation, and they all have to get from one end to the other, in the correct order, with none of them lost, and with minimal delay getting there.
You can think of VoIP in a manner similar to how a courier works. You have several parts which the factory (your voice) needs send somewhere to be assembled (the phone of the person you’re talking to). Each part is sent as soon as it is built, so the sending starts before all the parts are complete. You address a package, and it is picked up, placed on a truck, taken to the sorting facility, put in a crate, on an airplane, and then carried with all sorts of other traffic to somewhere near the destination, where it is taken off the plane, out of the crate, and placed on a truck where it is eventually delivered. At the other end, each packet is opened, and the part inside is added to whatever is being made from all the parts. When all the parts have arrived, you have a finished product!
When it works, it’s invisible to us. When it doesn’t work, it drives us nuts.
Ten years ago, it mostly didn’t work very well. Today? It works very well indeed. Most network equipment is now aware of the unique needs of voice traffic, and excellent quality VoIP is normal in any well-designed network.