As best I understand it . . . and I am a musician with nearly eighty songs currently copyrighted . . .
(and note, I got this next quote from
http://www.copyright.com/CopyrightRe...istration.asp, in case someone wants to lynch ME

)
"Your work is automatically protected under U.S. copyright law from the moment of its creation. Thus filing a copyright is not generally mandatory. However, filing does offer certain legal benefits, and it is required in order to file suit for infringement."
So here's how I would define it.
- If you had a song/lyric/webpage design registered with the copyright office, and someone ripped you off, you could sue and collect compensatory damages for the trouble the infringement caused.
- If you DON'T have a song/lyric/webpage design registered with the copyright office, but you have proof that you were the first to use such material (if, say, you mailed yourself proof via postmark, like the guy did with the Game Show scandals in the fifties) then you have the right to say "I own this, stop using it" and they must comply, but you lose the right to sue for damages.
The other thing is that once you've filed . . . even though the process takes eight to ten months to finish . . . your works are copyrighted officially the day you sign the forms.
Hope this helps!