What does it mean that there is a nail behind the latest Netease cloud listening song?

This flag indicates that the song or song list has been "collected".

In the latest version of Netease Cloud Music, there is a nail icon behind the listening list, indicating that the song or song list has been "collected". Users can collect their favorite songs or songs or song lists that they often listen to, so that they can listen to and find songs directly when they want to listen next time. To cancel the collection, just click the nail icon again.