Same thing, but the ATAPI is an improvement over the traditional IDE/ATA. One of the problems with the original ATA standard was that it only supported hard drives. Other devices like CD-ROMS, floppies, etc. were attached to proprietary interfaces. For example, many original CD-ROMs were connected directly to the sound card. In general, these interfaces proved to be slow and provide a burden to the card. To resolve this issue, a new standard was developed called the AT Attachment Packet Interface (ATAPI). It allows the devices to plug directly into a standard IDE cable and be configured like a ATA drive as a master or slave.