Pick the format by job
MP3 is the safest shareable audio format. WAV is better for editing and production. FLAC is best when you want lossless quality without raw WAV size. AAC and M4A work well for mobile and Apple workflows. OGG and OPUS are strong for web, games, and efficient voice or streaming use cases.
If you only need to send someone a playable file, MP3 is usually enough. If you need to keep a master file, keep WAV, AIFF, or FLAC.
Lossy and lossless conversion
Converting from a lossy file like MP3 to WAV does not recreate the lost audio detail. It creates a WAV container from the audio data that remains. That can still be useful for editing, but it is not the same as a studio master.
For music archives, convert from a lossless source when possible. For quick publishing, convert to MP3, AAC, or OPUS depending on where the file will be played.
Practical recommendations
Use MP3 for universal sharing, WAV for editing, FLAC for archiving, AAC or M4A for mobile delivery, and OPUS for efficient speech and web audio. After conversion, listen to the quiet parts, loud parts, and transitions to catch clipping or artifacts.