The Røde SC15, SC19, and SC21 cables are used to connect USB-C capable devices like the Røde Wireless GO II and the Røde VideoMic NTG to your iPhone with the Lightning connector. This connection makes it possible that the audio signal which got converted to a digital signal by the mic can be sent to the phone in digital form as well. This enables recording stereo tracks (which usually is not posssible over TRRS connectsions) as well as monitoring features.