What does this mean in Nocturne Op. 9, No. 2?

[powertoold]

Hello, I am not sure what this notation means in the sheet music. Would anyone please help me?

Thank you!

[wotgoplunk]

It's an ornament, in this case a turn.

Play the note above, the principal note, the note below, then the principal note again.

When you have accidentals though, the symbol above the turn tells you what to do to the upper note, and below tells you to do to the note below.

So in this case play Dflat-Cnatural-Bnatural-Cnatural

Here for more info: https://www.dolmetsch.com/musictheory23.htm

[powertoold]

Thanks for the link!

I am wondering, isn't it supposed to be:

D_flat, C_nat, B_nat, C_nat since the note right before the turn is a C_nat?

Thanks again!

[wotgoplunk]

Thanks for the link!

I am wondering, isn't it supposed to be:

D_flat, C_nat, B_nat, C_nat since the note right before the turn is a C_nat?

Thanks again!

Haha, yes it is. My fault! 

[contrapunctus]

Of course in romantic period music you start ornaments on the principle note rather than the upper auxilliary. You actually have a five note ornament there, so start in the C and then go up to the Dflat, back to the C, B, C.
This edition implies the four note turn, but that is just because it is not high quality.