Immutable types are normally thought of as just value types. With value types, it makes sense that when they are set, you don't want them to change. But you can also have immutable object types and immutable data structure types. Immutable types are a type whose internal state does not change once they have been initialized.
The behavior of immutable types does not astonish or surprise fellow programmers and so conforms to the principle of least astonishment (POLA). The POLA conformity of immutable types adheres to any contracts made between clients, and because it is predictable, programmers will find it easy to reason about its behavior.
Since immutable types are predictable and do not change, you are not going to be in for any nasty surprises. So you don't have to worry about any undesirable effects due to them being altered in some way. This makes immutable types ideal for sharing between threads as they are thread...