PCD (standing for Photo CD) is a Kodak proprietary graphics format for storing images on CDs. Ususally, the PCD image format is used for saving the photos scanned when using Kodak processing hardware.
Although the PCD graphics format was created to meet a wide range of photographic requirements, photo enthusiasts will typically convert this type of files to other, more popular, image formats.
Becasue PCD is not a highly popular format, users will prefer to convert their PCD image files to more common graphic formats, support by more graphic converter apps.
Users may also rely on PCD converters to quickly preview their images and select the desired output format.