Bit depth
In general, bit depth refers to the number of bits available for representing a “unit” of some digital data. For example, bit depth may be used to describe how many bits are available per pixel in an image: 1-bit would be 2 colors, black and white. (A QR code would be a real-life example.)
In audio engineering, bit depth refers to the number of available bits for each sample.[1] A larger bit depth means that the audio signal level’s true value can be represented more accurately.[2] That is to say, a larger bit depth will lead to a larger dynamic range.
Each additional bit adds about 6 dB to the dynamic range. Thus, a 16-bit resolution gives a 96 dB dynamic range and a 24-bit resolution gives a 144 dB dynamic range. This value also represents the signal-to-noise ratio (SNR). That is, 24 bits gives an SNR of 144 dB.[3]
A depth of 16 bits is sufficient for listeners, but a depth of 24 bits is recommended when working with audio as the noise floor may be increased when working with tools like compression.[4]
[1]: Brown, Griffin. “Digital Audio Basics: Audio Sample Rate and Bit Depth.” iZotope, 2021-05-10, https://www.izotope.com/en/learn/digital-audio-basics-sample-rate-and-bit-depth.html.
[2]: thompson-2005 p.368.
[3]: thompson-2005 p.369.
[4]: iZotope, Inc. “Bit Depth | iZotope Pro Audio Essentials .” YouTube video, 2:41. 2016-04-25. https://youtu.be/ubCMI3Jq6e4