What is bandwidth in communication systems?

Bandwidth is the range of frequencies a communication channel can transmit, measured in Hertz (Hz). It determines the maximum data rate a channel can support (Shannon's theorem: C = B*log2(1+SNR)). Greater bandwidth allows higher data rates and better signal fidelity. For analog signals, bandwidth is the range from lowest to highest frequency component. For digital signals, bandwidth relates to symbol rate and modulation scheme. Bandwidth is a precious resource, allocated by regulatory bodies.