Tacit's response above was indeed a concise summary of the basics. To address some of your subsequent questions:
**What's "airplane mode" that seems to pop up in discussions as a protective measure?
Airplane mode, with just one tap, is way to set the phone so that it does not send or receive via wi-fi, Bluetooth or a cellular network. So named because when flying it seems that the take-off and landing environments do not want any extraneous broadcasts to interfere with communications involving the plane. Once above 10,000 feet the phones can be returned to their normal state.
**How does one prevent excessive charges when globetrotting?
Ahh, would that this had a simple answer. Well, maybe it does—turn the phone off!
In practice one must decide from where their charges arise. For most people it is when they are using the phone company's cellular network (beyond some plan allocation of data), as opposed to a wi-fi network. As Tacit said above, roaming is the additional killer. So when globetrotting, turn off cellular and only use wi-fi. This could limit your ability to use the phone as a phone, although there are "telephone talking apps" that work on wi-fi (e.g., Skype, TruePhone, Facetime).
Additionally one could purchase an international phone plan from your own provider, or purchase a SIM card (the removable goodie in the phone that, among other things, helps to identify the provider and network) in the country of travel.
**Why do providers not provide a single package price for all use? I suspect the answer is obvious — namely whatever the traffic will bear.
This may happen eventually. We have seen land lines go from long distance charges to free nationwide calling. The same has happened with cell phone services. Most have basic packages that also offer unlimited text messages. The primary cost to the consumer is data outside of calls and texts. Perhaps this is because providers want to control or profit from the amount of traffic. If the day comes that the network is blazingly fast for everyone, then perhaps the cost structures will once again change.
