This refers to the frequency range a device can carry without degrading any of the information. It's also used in digital communication to show how much information something can transfer over a given time.
Audio Bandwidth for a device recording at 48 kHz will have a bandwidth of 24 kHz. This is due to the The Sampling Theorem which roughly states that you need at least 2 points of measurement for the highest frequency waves to be properly represented digitally. Recording at 10 kHz sampling rate would be able to capture 5 kHz before loosing information.