Bandwidth means how much maximum data transfer rate can be on a network or Internet connection.
It measures how much amount of data can be sent in a specific connection, that too within a particular time. For example, a gigabit Ethernet connection has a bandwidth of 1,000 Mbps, (125 megabytes per second). The internet connection via cable modem has a bandwidth of around 25 Mbps.
Where bandwidth is used to describe network speeds, bandwidth does not measure how fast bits of data move from one location to another.
Since data packets travel through electronic or fiber optic cables, each bit is tranferred to each bit, their speed is absolutely negligible. At the same time, bandwidth measures how much amount of data travels through a specific connection at the same time.
If we visualize the bandwidth, then in such a way you can think of a network connection at the top of a tube and every bit of data inside it can be considered as sand particles. At the same time, if you pour a lot of sand into the tube thinly, then it will definitely take more time to move the sand through it.
Whereas if you pour the same amount of sand into a small tube, then that sand will run through it very soon.
Just like this, if you have a high-bandwidth connection, then the download in it is much faster and less in the low-bandwidth connection.
Data flows across multiple network connections most of the time, which means that the connection that has the least bandwidth is considered a bottleneck.
For example, the bandwidth between Internet backbone and connections servers is the highest, so they rarely serve as bottlenecks. The most common common Internet bottleneck is your connection with your ISP (Internet Service Provider like Jio , Airtel , BSNL broadband etc.).
NOTE Bandwidth is also a range of frequencies that are used to transmit a signal. This type of bandwidth is measured in hertz and is mostly referenced in signal processing applications.