Mutability, simply put: the contents of a mutable object can be changed, while the contents of an immutable object cannot be.
All of the simple data types we covered first are immutable
For the mutability of the container types we covered in this chapter, check this helpful list:
||ordered group of items, accessible by position||yes|
||mutable unordered group consisting only of immutable items. useful for set operations (membership, intersection, difference, etc)||yes|
||contain ordered groups of items in an immutable collection||no|
||contains key value pairs||yes|