Internet Small Computer System Interface is a transport layer protocol that describes how Small Computer System Interface (SCSI) packets should be transported over a TCP/IP network. iSCSI, which stands for Internet Small Computer System Interface, works on top of the Transport Control Protocol (TCP) and allows the SCSI command to be sent end-to-end over local-area networks (LANs), wide-area networks (WANs) or the internet. IBM developed iSCSI as a proof of concept in 1998 and presented the first draft of the iSCSI standard to the Internet Engineering Task Force (IETF) in 2000. The protocol was ratified in 2003.
iSCSI makes it possible to set up a shared-storage network where multiple servers and clients can access central storage resources as if the storage was a locally connected device.
Source: https://searchstorage.techtarget.com/definition/iSCSI