Bit depth determines the dynamic range of a digital audio recording — the difference between the quietest and loudest sounds that can be captured. Each additional bit adds approximately 6 dB of dynamic range. 16-bit audio (CD quality) provides 96 dB of dynamic range. 24-bit audio provides 144 dB of dynamic range.
For recording, 24-bit is the standard across all modern audio interfaces. The extra headroom compared to 16-bit means you can record at slightly lower levels without running into the noise floor, making it easier to recover from minor gain staging mistakes without audible distortion or hiss.
24-bit recordings are commonly dithered down to 16-bit for final delivery (CD, streaming). Dithering adds a tiny amount of shaped noise to mask quantization artifacts — the result sounds significantly better than simply truncating the extra bits.
32-bit float is a newer format appearing in some portable recorders and interfaces. It records with so much headroom that clipping is virtually impossible regardless of input level — a significant advantage for live recording where levels cannot be monitored in real time.