Bandwidth is the maximum rate of transfering data along its given path.
Bandwidth can usually be defined as the bits that can be sent in 1 second.
The bandwidth here, is displayed as connection "speed", with the unit being megabits per second, on a PS4 connection test.
Bandwidth can also be described as ones ability to deal with a situation, espicialy one with a large amount of information.
Although bandwidth is how much information is being sent, it isnt' necessarily the speed of which it is being sent.
There is more to bandwidth than just this a good source of information would be Wikipedia.