What is the difference between wideband and narrowband?

In the Narrow-band channel the signal see the channel as a flat channel , and the signal pass the channel without any type of cut .

In the other hand the signal that passes through the wide-band channel see the channel as a frequency selective channel and cut values from the signal .

I mean that if the bandwidth for the signal is lager than the bandwidth for the channel then, the channel is a wide-band channel, and if the bandwidth for the signal is smaller than the bandwidth for the channel then the channel will be a narrow-band channel .