What does .ogg extension mean?

Question

in the audio tag SRC doesn't know .ogg extension

Answer 1

The file with the .ogg extension contains multimedia data in a bitstream format.

.mp3 and .mp4 are similar file formats.

BTW: the MIME Type should be 'ogg - audio/ogg' or 'application/ogg'

Answer 2

The ogg project wants to build a free software usable in digital multimedia. It is defined in RFC 3533. This format contains sequences of codes named pages recognisable by the "OggS" keyword. It is used for audio and video so as for text codecs

Answer 3

https://en.m.wikipedia.org/wiki/Ogg