OGG Vorbis
OGG Vorbis is an open audio format developed as a patent-free alternative to MP3. macOS does not play OGG files natively. Use VLC Media Player to play recovered OGG files.
What File Juicer does with OGG files
File Juicer does not carve OGG files out of other files. What it does is recognise OGG files by their file header when the extension is missing. This is useful for files recovered from browser caches, where files are stored without their original extensions.
OGG on the web
OGG Vorbis was used in HTML5 <audio> elements mainly before 2017. Firefox at the time would not play MP3 due to patent concerns, so some sites provided OGG as an alternative audio format alongside MP3. After the MP3 patents expired in 2017, OGG use on the web declined and it is now rare. Browser caches from sites that used OGG are the most likely place to encounter these files.