Bandwidth
How much data can be transmitted in a time period over a communications channel, often expressed in kilobits per second (kbps).
The difference between the highest and lowest frequencies available for network signals. The term is also used to describe the rated throughput capacity of a given network medium or protocol. In short, bandwidth is a loose term used to describe the throughput capacity (measured in Kilobits or Megabits per second) of a specific circuit.
The difference between bandwidth and data transfer causes much confusion and is worth noting.
Bandwidth is a rate and data transfer is a total. For example, you might buy bandwidth of 128 kbps for a maximum monthly data transfer of roughly 40 GB.
Statistically, most sites use less than 500 MB per month, which is 1/2 of one gig. Unless you are offering software or music or video downloads or are just very popular, you shouldn’t have to worry too much about bandwidth.