Lossless vs. lossy
WAV and FLAC keep every sample; MP3 and AAC make much smaller files by permanently discarding less noticeable detail.
See it
What it is
A lossless file can reconstruct every original audio sample exactly. A PCM WAV usually stores those samples uncompressed, while FLAC and ALAC pack them smaller without throwing any away. Lossy formats such as MP3 and AAC save much more space by discarding detail their encoder predicts people are least likely to notice. MP3's encoder was tuned at Fraunhofer partly against Suzanne Vega's Tom's Diner, because a bare unaccompanied voice made every artifact obvious.
Keep recording, editing, archives, and delivery masters lossless. Make lossy copies for streaming, downloads, email, and other places where bandwidth matters. At sensible bitrates AAC and MP3 can sound excellent, but they are endpoints, not working masters.
Gotcha: converting an MP3 to WAV does not restore what the MP3 encoder removed; it only puts the damaged result in a larger container. Repeated lossy exports stack artifacts too. Generate every delivery copy from the original lossless master, never from yesterday's MP3.
Ask AI for it
Create two delivery copies directly from the original 48 kHz 24-bit PCM WAV with FFmpeg. Encode the archive copy with `-c:a flac` and the web copy with `-c:a aac -b:a 192k`; do not derive either one from the other. Verify sample rate and channel count with ffprobe, compare both outputs against the WAV, and label the FLAC lossless and the M4A lossy in the filenames.