SPDIF is an acronym for Sony-Phillips Digital Interface. Very similar to AES/EBU standard but uses unbalanced cables.  SPDIF may be converted to AES/EBU. This is a common digital interface which transfers two audio channels over a single unbalanced cable. Commonly uses phono or RCA connectors. For best results it is suggested that co-axial video cable be used. (For this reason some products use BNC video connectors for SPDIF)
Although commonly used for digital audio, S/PDIF may also be used to synchronize digital devices.