System Setup : File Format, Bit Depth, and Sample Rate : Bit Depths
 
Bit Depths
While Pro Tools | First records and plays back all audio at 32-bit floating point, it can import and export audio files at 16-bit, 24-bit, and 32-bit floating point.
16-Bit
CDs (Compact Discs) use 16-bit.
24-Bit
24-bit for audio files is commonly used for most music production and post-production projects with multiple audio tracks, mixing, and plug-in processing.
32-Bit Floating Point
32‑bit floating point bit depth lets you avoid clipping and unnecessary dithering with AudioSuite rendering. It also helps avoid rounding errors in signal processing (which can occur during bit depth conversion for file playback and real-time plug-in insert processing).