Bandwidth is a broad term defined as the bit-rate measure of the transmission capacity over a network communication system. Bandwidth is also described as the carrying capacity of a channel or the data transfer speed of that channel. However, broadly defined, bandwidth is the capacity of a network. Bandwidth exists in physical or wireless communication networks.
Techopedia explains Bandwidth
Data is sent over a network from a source and is received by a node at its destination. Imagine that each side of the transmission has a modem with a different data rate. For example, the modem on the source side might be 256 Kbps, while the modem on the destination side is capable for 128 Kpbs. This will not be a good combination for efficient communication as both ends have different data transfer rates, which ultimately causes delays in communication.