The iPhone 5 is Apple’s first mobile handset that uses new “LTE” wireless networks. What’s LTE —and why should you care? Here are some answers.

Q: What does LTE stand for?

A: It’s “Long-Term Evolution,” but that doesn’t really tell you anything. It’s actually the latest and fastest way to transmit data from cellular towers to phones and other gadgets. It’s one of two so-called “fourth-generation,” or 4G, wireless technologies that have been deployed by various phone companies. (The other one is WiMax, which is available on Sprint phones. But WiMax coverage is low, isn’t being expanded, and even Sprint is betting on LTE for the future).

Q: How fast is LTE? Will it make a difference to me?

A: LTE networks in the U.S. reach speeds up to 20 megabits per second. That’s faster than most people get at home, with their cable or DSL services. It’s also faster than older wireless networks, but the differences aren’t always that big. Sprint and Verizon iPhone users should see a huge jump in speed with the new iPhone because their 3G networks are relatively slow. Downloads will be more than ten times faster where LTE is available. For AT&T users, downloads speeds should double or triple.

Q: Which phone companies have LTE, and where can I get it?

A: Verizon Wireless launched its LTE network nearly two years ago. It has the widest coverage, by far: 370 cities. AT&T is second, with 62 cities. Sprint is only in the early stages of its buildout, and LTE coverage is spotty, for now. It covers 19 cities, mostly in Texas and Georgia. But Sprint has said that it plans to fire up New York, Washington, Boston, Los Angeles and some other cities in the next few months.

Q: My iPhone 4S already says it connects to “4G.” Doesn’t that mean LTE?

A: No, AT&T jumped the gun a bit and called its upgraded, non-LTE network “4G” because the speeds were so much higher than before. Apple went along with this, so the AT&T iPhone 4S displays “4G” in the status bar at the top of the screen even though it’s connecting to a 3G network.

Q: Is the iPhone 5 the first LTE phone?

A: No, Apple hasn’t been a trailblazer here. The first LTE phones showed up a year and a half ago, from other manufacturers such as Samsung and HTC. This year, it’s become a standard feature in high-end smartphones.

Q: Verizon and AT&T have been using different types of networks. Now they’re both on LTE. Does that mean I can move phones between the companies?

A: Unfortunately, no. They use different frequencies for LTE, and the iPhone 5 will come in two different versions. One connects to AT&T’s LTE bands, the other to Sprint’s and Verizon’s. (There will be a third one for overseas LTE networks.)

Q: Is there any downside to LTE?

A: Not really, but as you go from 3G to LTE, you might want to keep a closer eye on your data consumption for a while. Surveys show people have higher data usage on LTE, possibly because it lets you download more stuff, faster. It also makes it easier to enjoy video streaming and videoconferencing. AT&T and Verizon now limit monthly data usage (in practice, even for people who have the old “unlimited” plans), while Sprint still provides unlimited data.

Early LTE phones had shorter battery lives, but the chips now draw less power, and Apple promises the same amount of effective use time on LTE as on older networks.

Q: Will the LTE capability mean anything for phone calls?

A: For now, LTE networks carry only data, so the iPhone 5 will use older networks when connecting calls. In the future, LTE will likely be used for calls as well, and it’s possible that could mean improved audio quality. (Apple has its own scheme for improving audio quality, unrelated to LTE. But it’s unclear if U.S. carriers will support it.)