Bandwidth is a measurement of information sent from and received by your site, and is measured in megabytes. For example if a single page size including graphics is 40kb, each time that page is requested you have used 40kb of the allowable bandwidth for the month.
The current bandwidth allotment for sites with their own domain is: 1 Gigabyte/month, thus in the above example the 40kb page could be served over 25,000 times before reaching your quota.
Sites residing under the QGM domain are limited to 100 megabytes/month.
Your daily bandwidth usage is recorded. At the end of each calendar
month, the month's data is collected, the highest value is dropped, and the remaining
days are averaged. If your average is then over the limits on your account, an
additional charge will appear on your next bill. It is extremely rare (unless you're lucky enough to have an immensely successful & popular site) to exceed the generous allotment of 1 gigabyte per month.