In general, broadband refers to telecommunication in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed and sent on many different frequencies or channels within the band concurrently, allowing more information to be transmitted in a given amount of time (much as more lanes on a highway allow more cars to travel on it at the same time).

Various definers of broadband have assigned a minimum data rate to the term. Here are a few:

Newton's Telecom Dictionary: "...greater than a voice grade line of 3 KHz...some say [it should be at least] 20 KHz."

Jupiter Communications: at least 256 Kbps.                                                        

IBM Dictionary of Computing: A broadband channel is "6 MHz wide."