what is core data
what is coredata
Core Data is an object graph and persistence framework provided by Apple in the OS X and iOS operating systems. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0. It allows
data organised by the relational entity–attribute model to be serialized into XML, binary, or SQLite stores.
See Apple's documentation titled 'What Is Core Data?"
https://developer.apple.com/library/watchos/documentation/Cocoa/Conceptual/CoreData/index.html