What is a .aiff file?

You're working with audio on a Mac and the file is an AIFF. This is Apple's uncompressed audio format — the macOS equivalent of WAV. Both store raw PCM audio at full quality, both produce enormous files (~10 MB per minute at CD quality), and both are functionally identical in everything except which ecosystem prefers them.

AIFF was developed by Apple in 1988, based on Electronic Arts' IFF format. It stores audio data in big-endian byte order (WAV uses little-endian), which is a technical distinction that matters to audio engineers and nobody else. Some AIFF files include metadata chunks for loop points and instrument data, which is why you'll encounter them in sample libraries and music production.

Every audio application on macOS handles AIFF natively — Logic Pro, GarageBand, QuickTime, Apple Music. VLC plays them on any platform. For sharing audio outside the Apple ecosystem, convert to WAV (universal uncompressed) or MP3 (universal compressed) with fwip. If someone sends you an AIFF and you're on Windows, VLC or Audacity will open it without complaint.