How does Second Space work? Oppo/OnePlus/realme phones have a feature called "System Clone" which sounds similar.
It is essentially a secondary user in your phone but it's very low key and helpful to protect your privacy from other people who might access your phone. You can access the System Clone by inputting a different PIN or Password from your main user's password. You can even set up different fingerprints for your main user and the system clone.
So depending on the fingerprint or PIN/password you enter, you enter either the main user or the System Clone. It also seamlessly transfers you to the main user if someone else enters your main user PIN while you had the phone locked in the System Clone user.