What function of .ogg is? I still don't understand

Answer 1

.ogg function??
You mean source tag?
That is for "when sound media of video is not loading"

Answer 2

.OGG is an audio format, like .MP3

Answer 3

.ogg is format for audio or video files :)
example:
<video>
<source src="video.ogg" type="video/ogg">
</video>

Answer 4

thanks guys