What is copy in Objective C?

-copy is required when the object is mutable.
-copy specifies the new value should be sent -copy on assignment and the old value sent -release.
-copy is  like retain returns an object which you must explicitly release (e.g., in dealloc) in non-garbage collected environments.
-if you use copy then you still need to release that in dealloc.
-Use this if you need the value of the object as it is at this moment, and you don't want that value to reflect any changes made by other 
owners of the object. You will need to release the object when you are finished with it because you are retaining the copy.

Example:
@property (nonatomic, copy) NSArray *myArray;
@synthesize myArray;