The Compact Disc (also known as a CD) is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage (CD-ROM), write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Discs (VCD), Super Video Compact Discs (SVCD), PhotoCD, PictureCD, CD-i, and Enhanced CD. Audio CDs and audio CD players have been commercially available since October 1982.
Standard CDs have a diameter of 120 millimeters (4.7 in) and can hold up to 80 minutes of uncompressed audio or 700 MB (700 × 220 bytes) of data. The Mini CD has various diameters ranging from 60 to 80 millimeters (2.4 to 3.1 in); they are sometimes used for CD singles, storing up to 24 minutes of audio or delivering device drivers.
when CDs are being scratch or heated in a sunlight, it will destroy the CD and you might throw that away.
Before throwing your old CDs away. There is so many things you can do with it.
Here is the sample Image that you can make out of CDs.
CD Wall Clock
This Video shows how to make a Wreath Out Of Old CDs