Bandwidth is the capacity of a wired or wireless network communications link to transmit the maximum amount of data from one point to another over a computer network or internet connection in a given amount of time -- usually one second. Synonymous with capacity, bandwidth describes the data transfer rate. Bandwidth is not a measure of network speed -- a common misconception.
While bandwidth is traditionally expressed in bits per second (bps), modern network links have greater capacity, which is typically measured in millions of bits per second (megabits per second, or Mbps) or billions of bits per second (gigabits per second, or Gbps).
Bandwidth connections can be symmetrical, which means the data capacity is the same in both directions to upload or download data, or asymmetrical, which means download and upload capacity are not equal. In asymmetrical connections, upload capacity is typically smaller than download capacity.
For Example: Bandwidth can be compared to the amount of water that can flow through a water pipe. The bigger the pipe, the more water can flow through it at one time. Bandwidth works on the same principle. So, the higher the capacity of the communication link, or pipe, the more data can flow through it per second.