what does this icon mean in a playlist?

[mrgreeneyes]

what does the downward face arrow mean? ( bottom right of screen shot)
I have this arrow on many of my playlist on my Mac, and some have a checkmark instead of the arrow.

 

[danmart]

Click the arrow to download to your machine; a tick mark means it has been downloaded already.

 

[Mr.Blacky]

The arrow means you can download this song/album/playlist to use it offline. A checkmark means it's downloaded.

 

[mrgreeneyes]

The arrow means you can download this song/album/playlist to use it offline. A checkmark means it's downloaded.

when I click on the arrow, nothing happens.