What is the difference between an audio cd writeable and normal one?

[Drengot]

Well, thanks for replying.
I generated the question after have tested in a very good hi-fi a little difference between an original cd and the copy on a tdk reflex 12x.
During the listening, the piano at the beginning of the 4th track of "Dark side of the moon" seemed to be a little bit weacker than in tihe original cd. I know that I'm speking about soft differences for wich personal feelings can play an important role. However, I began also to have problems of reading with my hi-fi and my car cd reader...so I thought that perhaps it would be better to use an audio cd. My car cd reader now has problems with copied cd but one month ago it was perfect with every cd...not only the originals like now!!!!!!
I hope to have not all these problems in the future!

Thanks a lot...

Drenogot