what is difference between mutable and immutable

Question

what is difference mutable and immutable

like

NSString and NSMutableString.

NSArray and NSMutableArray.

NSDictionary and NSMutableDictionary

Answer 1

Mutable can be changed, immutable cannot. When you share a mutable objects, you should expected the some one can change it. When you share an immutable object, you expected the no one will changed.