(FORTUNE Magazine) – Broadband. Short for "broad bandwidth," as in a high-speed network able to carry video as well as voice. Bandwidth describes the throughput of a network per unit of time, measured in kilobits, megabits, or gigabits per second.

Cable modem. A device that plugs into a cable network to provide Internet access to homes or small businesses. In theory, cable modems provide high-bandwidth service, up to ten megabits per second (10 Mbps), but because the cable line that runs down the street is shared with other users, the actual speed is comparable with that of phone lines using DSL.

Convergence. The end point of the digital era, in which all types of digital information--voice, video, and data--will travel over the same network. Leads in turn to divergence, the proliferation of small, single-purpose devices like MP3 players at the expense of the do-it-all PC.

DSL. Short for "digital subscriber line," a high-bandwidth Internet access service that works over standard phone lines. Subscribers must live within a certain distance of the nearest telco switch. DSL exists in many flavors, but the most common type is ADSL, or asymmetric DSL, in which signals from the Web to your computer travel faster than the other way around (6.1 Mbps vs. 640 Kbps).

Edge. The boundary between the local network and cyberspace. It refers to a way of getting around Internet bottlenecks: that is, to move digital libraries from centralized servers to caches at the margin, or edge, of the network, nearer to subscribers.

Fiber to the home. The dream broadband network: fiber-optic cable all the way to your front door. A handful of companies are beginning to build such networks, but it will be a long time before a bungalow on the South Side of Chicago gets its own fiber connection.

Free-space optics. Also known as wireless fiber, this technology uses lasers and optical transceivers to send signal-bearing photons directly through the air instead of over fiber-optic glass.

IP. Short for "Internet protocol"--the rules that govern how all the networks constituting the Internet exchange packets of data and route them to their destinations. Think of it as the equivalent of the universal addressing convention for snail mail.

Last mile. The link between your home and the nearest aggregation point of your communications network, like a telco central office or a cable-system head-end. It's the service you have on this piece of the network that usually determines the speed of your Internet connection.

MP3. A standard for storing music in digital format. MP3 compresses music files by a factor of 12 with little audible change in quality, making them easier to store and to transmit across the Internet.

Open access. A hot topic as cable companies provide Internet access to more homes. Phone companies, as common carriers, must let any company provide Internet access over their networks, but cable companies have so far been free to keep the ISP market all to themselves.

Packet network. One in which each signal, whether it carries music or video or e-mail, is chopped into tiny digital parcels that are commingled with hordes of other packets, routed to their destinations, and then reassembled. The Internet is a packet network. The phone system is a circuit network, where each signal travels unbroken on its own end-to-end pipe.

Photonics. The science of photons, or light. Optical networks will be the hallmark of the broadband era, and over the next decade photonics will become as much a part of the popular lexicon as electronics is today.

Streaming media. In theory, it's like listening to radio or watching television but with a signal that travels over the Internet. In reality the quality can be woeful, but it's getting better as bandwidth increases.

Throttling. Ever rent a truck with a governor that keeps you from going over 55 miles an hour? Telcos and cable companies do the same with high-speed Internet service, restricting the maximum speed of your DSL or cable- modem connection to conserve their network bandwidth.

Walled garden. The practice by which an Internet service giant like AOL gives customers easier access to its own and its partners' content than to that of its competitors. The European Union has hinted that it might object to the AOL/Time Warner deal for this reason.

WAP. Short for "wireless application protocol." With WAP, Internet companies will need to configure their content only once, and it can then show up on the tiny screen of almost every wireless device, regardless of service provider.

--Eric Nee