A SCSI device does not initiate a session, but waits for a command from other device, is called :

In SCSI architecture, a Target is the device that responds to commands from an Initiator. The Initiator (usually the host computer) starts the SCSI session and sends commands to the Target (usually a peripheral device like a disk drive). The Target passively waits for commands and executes them. A LUN (Logical Unit Number) is an addressable entity within a Target, not the device role itself.