Bandwidth refers to the transmission capacity of a communication channel. It is the amount of data that can be transferred in a specific amount of time over a network connection. Bandwidth is measured in bits per second (bps), and it determines the speed at which data can be transmitted over a network. The higher the bandwidth, the faster the data can be transmitted. This is important for applications such as video streaming, online gaming, and large file transfers that require a lot of data to be transmitted quickly.