The technical definition of "bandwidth" involves the difference between two frequencies and the amount of information that can flow through a channel, as expressed in cycles per second (hertz). It also refers to the range of frequencies (not the speed), or the measured amount of information, that can be transmitted over a connection: the higher the frequency, the higher the bandwidth and the greater the capacity of a channel to carry information. For a digital channel, bandwidth is defined in bits per second (bps). For an analog channel, it is dependent on the type and method of modulation used to encode the data. Broadcast TV channels, for example, all have the same bandwidth, by FCC rule.
In Web jargon, you may hear bandwidth described as the amount of time it takes for a Web page to fully load. Even though this notion is widely used, it is fundamentally incorrect. You will also hear bandwidth refer to the amount of traffic on a Web site, but again this is actually not accurate. One reason why these ideas proliferate is because Internetusers refer to larger graphics as "bandwidth hogs," meaning they take up so much room that the download is very slow.
In real life, the term bandwidth has made it's way into mainstream slang. It is often heard around the office to describe tech exec's inability to think about or do multiple things at once, as in, "I don't have the bandwidth to deal with your request right now." If a person is described as having "low bandwidth," it means he or she is considered slow on the uptake ;-)