Mobile phones are becoming the Swiss Army knives of modern gadgetry. Merely making phone calls is so 2004. Surfing the Web at near-broadband speeds, storing crucial work files, editing memos — these are things that people can, or soon can, do right on a phone.

The problem is that it’s more and more confusing to sort through the options. Phone store salespeople and Web sites spout indecipherable acronyms, different phone carriers sell wildly varying services and add-ons, and some new technologies bring security worries along with them. So here’s a quick primer on what the modern cellular user needs to know, right now.