Immutable: The state of the object cannot be changed after creation
Example: String , you can’t change it after it is created. It looks like you can, but what happens is that a new string is created.
Mutable: The state of the object can be changed after creation
Example: Stringbuilder , you can change this object after you have created it. You can append, remove, replace, or insert characters to the same object,- a new one isn’t created as with String.