Sample rate describes time
A PCM sample rate is the number of amplitude measurements represented per second. CD audio uses 44.1 kHz; video-oriented systems commonly use 48 kHz. Higher-rate files may use 88.2, 96, 176.4, or 192 kHz. The 44.1 and 48 kHz families matter during playback because converting between them requires resampling.
A file can have a high sample rate without containing useful high-frequency information. It may have been recorded that way, processed at that rate, or upsampled later. The number alone does not reveal the history of the master.
Bit depth describes each PCM value
Bit depth sets the number of values available to represent a PCM sample. It affects quantization resolution and theoretical dynamic range. A 24-bit file can preserve additional production headroom, but playback quality still depends on the source, mastering, gain changes, and output path.
Decoded audio may also move through floating-point processing. Nyquist's PCM engine uses a 32-bit float mixer, which is one reason sample-rate matching should not be confused with proof that every original integer bit reaches the output unchanged.
Lossless is a separate question
FLAC and ALAC are lossless codecs; MP3, AAC, Vorbis, and Opus are lossy codecs. Any of them can carry audio labeled with a sample rate. A 192 kHz label does not reverse information removed by an earlier lossy encode, and a 44.1 kHz FLAC can still be a fully lossless representation of its source PCM.
What Nyquist shows
Nyquist reports the file's detected codec, sample rate, bit depth, and channels. On macOS, it can ask a selected CoreAudio output device to use the file's rate or a clean same-family multiple, wait for the device clock to settle, and report the resulting output rate and whether resampling was detected.
On iPhone, iPad, and Apple TV, the operating system controls more of the final route. Bluetooth, AirPlay, built-in outputs, and individual receivers can impose their own limits. The source numbers and output numbers answer different questions, which is why Nyquist displays both.
Next: what bit-perfect audio actually requires or how Nyquist presents the signal path.