What does immutable and readonly mean in C#?

Question

Is it correct that it is not possible to change the value of an immutable object?

I have two scenarios regarding readonly that I want to understand:

Answer 1

Marking a field as read-only only means that you cannot change the value of that field. It has no bearing on the internal state of the object there. In your examples, while you would not be able to assign a new metadata object to the _metadata field, nor a new ICollection to the _items field (outside of a constructor that is), you can change the internal values of the existing objects stored in those fields.