Animoji and Memoji are animated emoji that mimic your facial expressions using your iPhone's forward facing camera. While most adults are probably not going to converse with animated emojis, kids definitely delight in them. Unfortunately only the iPhone X or later, iPad Pro 11-inch or iPad Pro 12.9-inch (3rd generation) can create and send Animoji and Memoji (though any iOS or Android device can receive them).
You can change the look of your Memoji at any time from the Messages app. Just tap the Memoji icon (3 faces) in the apps tray, then tap the 3 dots in the upper right hand corner from the pop up menu screen.
In addition to adding a few new Animoji and introducing Memoji, which are basically personalized Animoji, iOS 12 lets iPhone X owners use both moji in FaceTime video calls. The new AR feature is similar to using the face-tracking filters offered by Snapchat - the Animoji's facial expressions will mimic yours (now including your tongue and winking gestures with iOS 12). Next time you make a FaceTime call, try slapping on a pig face or try out the newly added T-Rex. Here's how to do it on iPhone X:
In addition to adding several new Animoji including a tiger, koala, T-rex and ghost, and adding tongue detection, iOS 12 also introduces Memoji. Memoji are personalized avatars that essentially allow you to create an Animoji of yourself, letting you customize your head shape, skin tone, hair style, eyes, accessories and more. Like the other Animoji, Memoji require the TrueDepth camera and thus are only currently available on the iPhone X. Here's how to create and use Memoji on iPhone: