Hello to all, what is this little thing? What it does?

[John Robert Roberto]

Please see the attached image.
Look at the encircled red.

[Richard M Knight · Accepted solution]

It tells you what type of audio track it is. Can be: Standard, Adaptive, Mono or 5.1 surround.

[John Robert Roberto]

Thank you very much. God bless.
Even I overlay my mouse cursor, there is no pop-up alternative text that show what it is.