Web Hosting Bandwidth
As with any business, a term can have many different definitions, as is the case with Bandwidth. When talking about bandwidth with an ISP or data traffic in general, you are discussing the amount of information that can be sent through a network at a given interval. Most Internet Service Providers register their traffic speed in kilobits per second (kbps), or megabits per second (mbps).
Although you are dealing with the same internet - when a web hosting service use the term bandwidth it is typical that they too mean traffic sent over their network, however the interval is over the course of one month. Your web host may offer 45GB of bandwidth for your hosting account - meaning that over one month or billing cycle, you can push 45 gigabytes of information over their network/through your web site and be within your accounts limits.
What counts as Bandwidth?
What exactly counts as bandwidth traffic according to your host is determined by your terms of service and user agreement. In general, every element associated with your web site, and is accessible to be uploaded or downloaded is within this grasp. Each time you FTP documents or files, and each time an image or web page is viewed, you have used a portion of your bandwidth.
Do not be alarmed regarding your website and running over on your bandwidth limit. Most websites have images and web pages below 50k each. On a 45GB web hosting bandwidth account - you would have to download your 50k image/page/etc over 250,000 times.