Both actually. There are Hardware iSCSI initiators, and there are software iSCSI initiators. The hardware ones are cards which plug into the slots in the computer, where the software ones are software which runs on the computer.
iSCSI runs over your normal ethernet network, so they will look like normal LAN ports. One of the big selling points of iSCSI is that it works over your existing Ethernet network so you don’t have to purchase new Fibre Channel equipment to use it.