Q:

Task of NSManagedObject, NSManagedObjectContext, NSEntityDescription, NSPredicate, NSPersistentStoreCoordinator

i am new in ios field, read the tutorial related to above class from apple official website. 
But i can't understand what is actually job of the NSManagedObject, NSManagedObjectContext, NSEntityDescription, NSPredicate given class.  
so please help me. 
Thank You. 

A:

Apple should put a link to Core Data Core Competencies in the tutorial.