The term bandwidth is used to refer the data transmission capacity of the network. The greater the bandwidth the more the information can be transferred over that network at one time.
In the internet, which is connected by a group of more than one computer, It is the size of each network connection that determines how much bandwidth is available. For example, if you use a DSL connection to connect to the internet, you have 1.5 Mega bits (Mb) of bandwidth. Bandwidth therefore is measured in bits. Bits are grouped into bytes that form text, and other data that is transferred between the computer and internet.
For analog devices, the bandwidth is expressed in cycles per second, or Hertz (Hz) and for digital devices; it is expressed in bits per second (BPS) or bytes per second.