The focus of spintronics memory device that constitutes MRAM has so far been largely on two-terminal magnetic tunnel junction with spin-transfer torque magnetization switching, because of its superior area efficiency. In a number of cases, however, where switching speed and relaxed control of parameters are more preferred than the reduced area, three-terminal spintronics device is an equally, if not more, attractive alternative. Here 'three-terminal' refers to the number of terminals used for read and write operations. This configuration allows realizing high-speed and high-reliability device operation, suitable for replacement of semiconductor-based working memories such as SRAMs but with nonvolatility and reduced area to overcome issues of scaling limit and increasing power consumption . Two types of three-terminal devices are currently under development; one utilizes a current-induced domain wall (DW) motion and the other a spin-orbit torque (SOT) induced magnetization switching for their write operation. Here we review and compare their basic operation principles and the technological prospects.