An audio file format refers both to the structure used to store audio data on a computer or storage device and to the encoding used inside it. WAV, MP3, AAC, and FLAC are typical examples, but the file extension alone does not always tell you the quality or the compression method.
The format and the audio data are separate things
The file format decides how the audio data, the metadata, and the information about the file are laid out. Sample rate, bit depth, PCM, and AAC, on the other hand, concern how the sound itself is represented. Two files with the same extension can use different encoding and settings inside.
Uncompressed, lossless, and lossy
Uncompressed formats such as WAV containing PCM take up more space, but they suit editing and handing files over during production. FLAC’s lossless compression decodes back to the original PCM. Lossy compression such as MP3 or AAC keeps files small, but discards some information during conversion.
Do not judge by the extension alone
WAV, for example, is a container for audio and is generally used with PCM, but it is not limited to that. M4A likewise usually indicates the container, with AAC often sitting inside it. Check the format and settings the recipient asks for.
Choose by purpose
If you are handing files to mixing or mastering, choose WAV at the requested sample rate and bit depth. MP3 or AAC suit previews and small file sharing, and FLAC is a candidate when you want to store or distribute files without losing quality. Streaming services and video editors have their own requirements, so put the delivery spec ahead of any general best answer.
Keep the original when converting
Converting an already lossy MP3 or AAC into another lossy format does not bring back what was lost. Keep a master such as WAV as your production reference and make copies for each purpose. When you need to export several formats, you can use the audio format converter tool.
