Bandwidth is a measure of frequency range and is typically measured in hertz. In common usage "bandwidth" also refers to data (information) transmission rates when communicating over certain media or devices.

In computer networks, such as the Internet, bandwidth is a term often used to express data transfer rate - the amount of data that can be carried from one point to another in a given time period (usually a second). This kind of bandwidth is usually expressed in bits (of data) per second (bps).