Technically, bandwidth is a measure of the communications capacity, generally expressed as a rate of how fast data can be stuffed down an Internet pipe. You may recall another term, baud, once used to measure modem transmission speeds. But at higher speeds, a single state change may signal multiple bits, and the correlation fails. The term baud is seldom used anymore. While bandwidth may be similar to gas and electricity, several flavors of bandwidth are available to business and residential customers.
Most consumers get Internet access through a dial-up service.
They connect their telephone lines to the modem port on their PC and then dial the local number of an Internet service provider to reach the Internet. A standard PC modem converts analog phone signals to digital data transmissions for data coming into the PC and vice versa. It's the nature of the quality of that hardware that is responsible for the severe bandwidth limitations of dial-up Internet access. Yet, as the Internet has grown, so have the transmission rates. Individually or collectively, these high-speed access methods are often called broadband.