pathetique question

[nixo1000]

I was wondering what is that M looking thing above the G flat, in the 3rd page, 7th measure. I  have noticed in the recordings that phrase is played in a particular manner.

https://www.sheetmusicarchive.net/compositions_b/btsn13.pdf

[allthumbs]

In the piece you posted, it's a musical ornament called an 'inverted mordent'. Check out the explanation.

https://en.wikipedia.org/wiki/Mordent