[jasim]

The type system is a lot more expressive than the ones found in Java/C#/C++, thanks to Algebraic Data Types.

Yaron Minsky (Jane Street, largest OCaml user) coined the term "make invalid states unrepresentable" to explain how ADTs help in enlisting the help of the compiler to help us express our intent correctly, and Richard Feldman (NoRedInk, largest Elm user) has given an absolute gem of a talk that dives into that idea with relatable, concrete examples.

It is titled "Making Impossible States Impossible" and should clarify this concept nicely. https://www.youtube.com/watch?v=IcgmSRJHu_8