youtube copyclaim?

It's really stupid, but yeah you cant play copyrighted music.

Because if Billy Joel records an album, that goes through a record label.  That record label has drawn up legal documents about copyrights.  So the music that is sold on a CD or cassette tape is copyrighted music.  If you were to buy a license to be able to play that music, then the record label would see some of that money, and the license you bought allows you to legally play that music over a broadcast.

Basically any music that is recorded and sold through a record label, will be copyrighted.  But it's also their music, and they own the copyright to that music.  Same as if you made a custom painting, and you put your name on it, you would own the copyright for that painting you made.

Even the radio stations all have several different licenses.  And those licenses contain certain copyrights, and it allows them to be able to play music from the radio station.  For me even, I could spend, it was something like $300 a year for I think 3 different licenses, and it would've allowed me to play and broadcast many types of different artists music.  I found a guy I called on the phone and spoke with about it.

There's this virtual world called SecondLife.  In SecondLife you can go to a club and listen to music.  Only one problem, in order to *legally* broadcast that music, you need the licenses, otherwise that music is being broadcast illegally and if someone who hasn't given clearance to play that music hears it being played, well they can fine you for real money, take you to court, sue you etc. etc. and there were tons of clubs who just streamed music but didn't have any rights to play that music legally.

Same as if you downloaded music without paying for it.  There was a story years ago about a lady who downloaded something like 200 something songs a day, and was fined like $300,000.00 USD, because downloading music without paying for it, is illegal.

If the owner of the copyright of something on YT doesn't want it distributed freely, they can ask for it to be removed and sue whomever posted it there. Of course, many copyright owners couldn't care less, or may actually WANT you to freely distribute their stuff royalty-free. It is entirely up to them to decide.

That would be the Content ID claim you asked about. Here's more about it:

What is a Content ID claim?

If you upload a video that contains copyright-protected content, your video could get a Content ID claim. These claims are automatically generated when an uploaded video matches another video (or part of another video) in our Content ID system.

Copyright owners can set Content ID to block uploads that match a copyrighted work they own the rights to. They can also allow the claimed content to remain on YouTube with ads. In these cases, the advertising revenue goes to the copyright owners of the claimed content.

You as the viewer / listener can play music. The uploader is not allowed to use copyrighted songs without a license. 

No, it doesn't help the singer directly. You pay the record company for the license, and the record company pays the singer royalties and/or contractually obligated amounts of money. If you're not paying somebody for music, though, then how is the singer supposed to make money? Arguing that you shouldn't pay for music because the singer doesn't see most of the money is pointless, because your alternative is not paying them at all.