music files disappear from itunes playlists ???

I’m copying and pasting songs from a folder to an itunes playlist.



When I delete the folder I copied them from the songs can not be played from the playlist and have an exclamation point next to them.



What am I doing wrong. I thought when you copy an paste the original music file remains in the itunes music folder??

via iLounge Forums http://forums.ilounge.com/itunes-related-mac-pc-applications/279708-music-files-disappear-itunes-playlists.html