After the launch of iPhone X, you all may know that Face ID has been limited and it supports only one person.
Unlike Touch ID, the company did not provide any other option to let someone else register themselves on your device.
However, this problem does not seems to be with iOS 12. However, Apple did not proclaim about this latest feature during its WWDC keynote.
Now, iOS12 will allow you to introduce another “alternative appearance” for Face ID. Apparently, it is being introduced for people having a problem in using Face ID ( like people with glass will have a choice to alter their look).
It can also be used for a second user. Similarly, your partner or your child will have a access to your phone even if they do not know your password.
Its features are much different from that of Touch id, as it is not the same as true multi-user support.
Face ID also provides a feature to reset it, if you ever had/have any issue with it. It seems to be a big problem here, even though, the company is well aware of limitations of its technology.