What is iSCSI and what is an iSCSI initiator?
iSCSI is a block level protocol similar to fibre channel, but it is designed to work over ethernet connections. An iSCSI initiator is the software that allows a workstation to connect to an iSCSI target, or storage.
iSCSI differs from Ethernet because as a block level protocol you have a direct connection between your OS and storage.
This means you can format storage over an iSCSI connection as a HFS or NTFS volume. This also means you can create a SAN with iSCSI.
The reality is, this doesn't really happen anymore.
iSCSI is somewhat of a failed protocol. Everyone using ethernet connections just uses standard ethernet protocols, because quite frankly ethernet got a lot faster than it used to be.