A caddy is the plastic case that enclosed a CD-ROM disk in the period when players required them. Early CD-ROM disks were always enclosed in a caddy and the caddy was inserted in the player. More recent CD-ROM players, following the compact disc players, provide a tray on which you can directly lay the CD-ROM disk. A caddy is not to be confused with the so-called plastic "jewel case" that some CD-ROM disks come in. These are mainly provided for marketing and storage protection purposes.