What is a CD used for?
A CD is is used for compacting data into itself such as photos, movies and songs
A CD-R is a CD type used only for burning information to it. This information is permanently on the CD, and you will not be able to add any further information to it once the first burn occurs. A CD-RW, however, can be used multiple times. Specific formats, such as VCD are used for particular types of data (in the case of VCD, it is video).