When Apple first released more secure ways to lock/unlock your iOS devices, we got Touch ID. It let us register up to five separate fingers, which was something that allowed us to share access to our iOS devices with trusted family members(and friends, if you really wanted to).
Then comes the iPhone X; the most advanced mobile device Apple has ever released! But it came with a few hiccups, one of which being the inability to give someone else a face. This made unlocking the device more difficult for those unrecognized by Face ID. They had to wait for the facial recognition software to fail and then tap in a passcode manually.
With the release of iOS 12, that limitation is a thing of the past! You can now allow a second person to register their face with Face ID on your iPhone X, XR, XS, XS Max, and the new line of iPad Pros (11" & 12.9"). To set this up, go to Settings > Face ID & Passcode. Enter your passcode and tap Set Up an Alternate Appearance. Then give your iPhone to the person who should have access and have them follow the simple setup directions.