Bandwidth is a measure that reflects how much data can be transferred over a data communication channel.
In web hosting, the allowed bandwidth generally indicates how much data can be downloaded from your web site per month, and therefore indicates how many web pages and pictures your visitors are allowed to download. If the average amount of page views per visitor is assumed constant, the allowable bandwidth restricts how many visitors you are allowed to have per month.
Just as important, however, is how fast the communication channel between your web host and the Internet is. The amount of data that can be transferred per second is also called the bandwidth of this channel, and this bandwidth is shared by all the web sites hosted by the same provider. If this bandwidth is insufficient, you’ll sometimes notice a slow down in the display of your web pages. In most cases, however, such a slow down is more likely to be caused by an overload on the web server itself.