What does the cloud with the arrow going down mean in my music?

No. If your library has gone unexpectedly cloudy when it wasn't before see Empty/corrupt iTunes library after upgrade/crash.

tt2

Means you must download it to play. You have it stored in the cloud.

It means that song is stored in your cloud and clicking it downloads a copy you then can play again and again no data or airtime use, which ever is used. 😐

Will they Charge me again to do that?