Overview of regular CD-types :

• CDS = CD Single : 1-4 tracks or up to 8 mixes. Usually in slim case (instead of regular jewelcase).
• CDM = CD Maxi: often with extended/remixed versions not available on LP
• CD = Album CD (very common!)
• DCD = Double CD
• 2CDBOX, 3CDBOX, 4CDBOX, ... : several CD's
• CDE = CD Extra : a regular audio CD on which they have also put video clips (the video needs a computer to be played)
• LCDM = Limited CD Maxi.
• XLCDM = "eXtra Limited CD Maxi" - another example: XLCD = "eXtra Limited CD"
  For example: 'Depeche Mode-2000-XLCDM-Freelove'
• Promo / DJC / APO = Promotional edition (Promotional Copy / DJ Copy / AirPlay Only)

Source: MTRH's Guide