What is difference between NSArray and NSMutableArray?

    NSMutableArray (and all other classes with Mutable in the name) can be modified.
  
    So, if you create a plain NSArray, you cannot change its contents later (without recreating it).
      
    But if you create an NSMutableArray, you can change it
      
    E.g.  NSMutableArray has methods like -addObject: and -insertObject:atIndex:
          
    NSMutableArray is editable, where as NSArray is read-only