|Enabled for||Public preview||General availability|
|Admins, makers, or analysts, automatically||Aug 1, 2019||Oct 1, 2019|
By using access modifiers, you have control over where it can be called from, be it your own code or third-party code building on top of your code.
You can control access and encapsulation of your code by adding local/private, protected, internal, or public access modifiers to AL language elements. This is similar to the way C# uses access modifiers.
Access Property (docs)