SCSI is a bus technology that can be connected to "daisy Chained" allowing multiple scsi devices to be connected on the same bus . SCSI was really common back in the 80s and 90s. Typically, you could get a RAID controller and server with SCSI onboard. There are 3 types of SCSI devices available.
Singel Ended SE
Differential SCSI (HVD or Hig voltage differential)
LVD Low Voltage differential.
Connection is external or internal. Over time, there has been a development of the SCSI connectors, so today there are many different for speeds. Always always remember to Terminate the SCSI devices. Last unit on the SCSI bus.
Standard SCSI cable: Cable is 2-layer shielded and supplied with 2 pcs. 50-pin Centronics male connector. Cable is used for connecting SCSI devices and "Daisy chain" of several SCSI devices.