Answer:   Immutable means once you create a thing, you cannot modify it.
For example: If you want give new value to old value then it will discard the old value and create new instance in memory to hold the new value.

Answer:   An immutable object is defined as an object that cannot be changed after it has been created. For example - String.

If you want to assign give new value to string then it will discard the old value and create new instance in memory to hold the new value.