Known by its abbreviation,
CD, a compact disc is a polycarbonate with one or more metal layers capable of
storing digital information. The most prevalent types of compact discs are those used by the music industry to store digital recordings and
CD-ROMs used to store
computer data. Both of these types of compact disc are
read-only, which means that once the data has been recorded onto them, they can only be
read, or played.
Also see Understanding CD Burner Speeds in the Did You Know . . . ? section of Webopedia.