Bandwidth is the maximum amount of data a connection can carry in a given time, usually expressed in bits or bytes per second. It sets an upper limit on throughput for buses, cables and network links.
In practice
An external drive connected through an older USB port may copy files far more slowly than the same drive on a newer port, because the older bus offers less bandwidth. The drive itself has not changed; the pathway has.
Common confusion
Bandwidth is a ceiling, not a guarantee. Actual throughput is often lower because of protocol overhead, shared devices and the slowest component in the chain. It also differs from latency, which concerns delay rather than volume.
Why it matters to readers
Understanding bandwidth helps interpret specifications and set realistic expectations. A driver can make good use of available bandwidth but cannot exceed what the bus and device physically allow.
A closer look
Bandwidth is often shared. Several devices on one USB hub divide the available capacity between them, and wireless networks share airtime among all connected devices. A webcam and an external drive on the same hub can therefore affect each other. Specifications listing a maximum rate describe ideal conditions with a single device and short, high-quality cables.
