I'm having hard time understand what bandwidth really is? The book i'm using defines it as the width of a signal's spectrum (where spectrum is the range of frequencies in a signal). So, for example, I have a composite, periodic signal s(t) = 4/π[sin(2πft) + (1/3)sin(2π(3f)t)]. Then the bandwidth of this signal is 3f-1f = 2f. Lets say f = 1Hz, then bandwidth of our signal is 2Hz. What does this 2Hz represent? Ignoring distinction between absolute bandwidth and effective bandwidth, bandwidth is measuring the difference between the highest and lowest frequency of a signal. So, in our example the 2Hz is saying nothing more than that the difference between the highest frequency and the lowest frequency of our signal is 2Hz? How is this definition of bandwidth useful? As a practical matter, how does this relate to transmission media? Can a media that carries signals with a bandwidth of 2Hz carry signals with lower bandwidth also? I don't have a strong background in electronics(which is why I'm studying) so any help is appreciated!