Broadband in telecommunications refers to a signaling method that includes or handles a relatively wide range (or band) of frequencies, which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider the bandwidth, the greater the information-carrying capacity.

In radio, for example, a very narrow-band signal will carry Morse code; a broader band will carry speech; a still broader band is required to carry music without losing the high audio frequencies required for realistic sound reproduction. A television antenna described as "normal" may be capable of receiving a certain range of channels; one described as "broadband" will receive more channels. In data communications an analogue modem will transmit a bandwidth of 56 kilobits per seconds (kbit/s) over a telephone line; over the same telephone line a bandwidth of several megabits per second can be handled by ADSL, which is described as broadband (relative to a modem over a telephone line, although much less than can be achieved over a fibre optic circuit).

Broadband in analog video distribution is traditionally used to refer to systems such as cable television, where the individual channels are modulated on carriers at fixed frequencies.[2] In this context, baseband is the term's antonym, referring to a single channel of analog video, typically in composite form with an audio subcarrier.[3] The act of demodulating converts broadband video to baseband video. However, broadband video in the context of streaming Internet video has come to mean video files that have bitrates high enough to require broadband Internet access in order to view them. Broadband video is also sometimes used to describe IPTV Video on demand.

The various forms of digital subscriber line (DSL) services are broadband in the sense that digital information is sent over a high-bandwidth channel (located above the baseband voice channel on a single pair of wires).