Every piece of networking hardware and every communications circuit has a finite capacity to move information. This capacity is measured in bits per second (bps), and is commonly referred to as the bandwidth of the device or circuit.
Different technologies have different bandwidths. For example, Ethernet has a bandwidth of 10 Mbps, meaning it can carry up to 10,000,000 bits of information in one second. Fast Ethernet operates at 100 Mbps, meaning it can carry up to 100,000,000 bits of information in one second. Therefore, the bandwidth of Fast Ethernet is ten times the bandwidth of 10 Mbps Ethernet.