What is a collection in iOS?

A collection can be called as a container - is simply an object that groups multiple elements into a single unit. A collection is a Foundation framework class that is used for storing and managing groups of objects in Cocoa and Cocoa Touch. Collection primary role is to store objects in the form of either an array(NSArray,NSMutableArray), a dictionary(NSDictionary), or a set (NSSet,NSMutableSet) etc.