The amount of information that a connection to the Internet can process at any one time. You can think of bandwidth as the size of a pipe. If you have a small pipe, less water can pass through. If you have a larger diameter pipe, than more water gets through. If you have more bandwidth (a faster Internet connection) than more data gets through and the inverse is also true.

DSL and Cable have relatively large pipes where dial-up is a very small pipe. The bandwidth for a large site might be equivalent to a water main.