Broadband in telecommunications is a term that refers to a signaling method that includes or handles a relatively wide range 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, greater is 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 a modem will transmit a bandwidth of 64 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.
Read more here.