What are we talking about? The Camera traditionally used to take images with your iPhone® is referred to as the REAR Camera, located on the back or rear of the iPhone®. The Camera traditionally used for Selfies and FaceTime is referred to as the FRONT Camera, located on the front or face of the iPhone®.
iPhone® 4,5,6,6 Plus 7 and 8 are SINGLE LENS and have 1 REAR Camera and 1 FRONT Camera.
iPhone® 7 Plus, 8 Plus and X are DUAL LENS and have 2 REAR Cameras and 1 FRONT Camera