Sample rate is the number of samples of audio carried per second, measured in Hz or kHz (one kHz being 1 000 Hz). For example, 44 100 samples per second can be expressed as either 44 100 Hz, or 44.1 kHz.
Bandwidth is the difference between the highest and lowest frequencies carried in an audio stream. The sample rate of playback or recording determines the maximum audio frequency that can be reproduced, as shown below.
For audio work, bandwidth is normally about 20 Hz less than the highest recorded frequency, so for practical purposes they can be treated as the same thing. Hence the terms are used interchangeably here. The term bandwidth may be applied to the frequency content of an audio signal stream, or the frequency ability of audio hardware or software.