Face ID is a facial recognition system that replaces Apple's Touch ID fingerprint scanner on some devices. It uses sensors placed around the iPhone's camera to scan your face and, if the scan matches the data on file, perform actions such as unlocking the phone or authorizing an Apple Pay transaction.
iPhone Face ID – All the tips and tricks you need to know.
Face ID is used for many of the same things as Touch ID. The most important of these are:
Face ID is supported by the entire iPhone X series: iPhone X, iPhone XS and XS Max, and iPhone XR.
It’s safe to assume that, just as Touch ID started on the iPhone and was added to other devices like the iPad, Face ID will eventually make its way to other Apple devices, like the iPad.