On Sunday, Verizon will launch its new 4G (or fourth generation) network, which promises to deliver much faster downloading speeds than its current 3G standard. For many customers, however, "4G" is still a a mysterious concept. As David Goldman at CNN says the term "has become meaningless and confusing as hell for wireless customers." Here's a quick guide to the technology:

How is 4G defined?
Last month, the International Telecommunication Union, which defines wireless standards around the world, designated a 4G network as one that's "capable of download speeds of 100 megabits per second." That's quick enough to "download an average high-definition movie in about three minutes." According to Verizon, "users will be able to download 20 photos in 60 seconds or a two-hour movie in five minutes." (See a Network World 4G demo)

Besides speed, what makes it better?
The network may make it easier to "install the Internet in a wider range of gadgets, such as digital cameras, gaming systems, and picture frames." 

Isn't 4G already available on other networks?
Yes, but not as widely as the phone companies would have you believe. AT&T claims to have the "world's largest 4G network," but that network actually doesn't meet the international standard. (Further muddying matters, certain 3G networks are actually faster than the 4G network Verizon will roll out.) Meanwhile, Sprint sells multiple 4G-ready phones, like the HTC Evo, but doesn't offer a network like the one Verizon is launching. Given all the confusion over terminology, some tech commentators think that terms like "3G" and "4G" will fade in significance as early as next year.

How many people will be able to use it?
By the end of the year, Verizon's 4G network will be available to about 110 million people in 38 American cities and 60 airports. Initially, access will be restricted to customers with computers (equipped with a $100 plug-in accessory) and a monthly 4G data plan. In 2011, Verizon is expected to release the first smartphones designed to run on its 4G network.

Do you need 4G now?
"For consumers,"
says Sascha Segan at PC Mag, "4G is mostly about internet speeds... 3G will be just fine for most people through 2011, unless they absolutely demand ultimate speed." You might as well just wait until next year, agrees Dan Frommer at Business Insider: "4G is more likely to be a Holidays 2012 or 2013 story for most people than 2010 or 2011."

Sources: Business Insider, CNN, CNN Money, PCMag