Collections is framework which in which we can deal number of objects as single entity means that we create a Collections of any data type which is used in single common data form. Collections classes are specialized classes which are used for data storage and retrieval. These classes provide support for stacks, queues, lists, and hash tables. Most Collections classes implement the same interfaces. Collections classes serve various purposes, such as allocating memory dynamically to elements and accessing a list of items on the basis of an index etc. These classes create Collections of objects of the Object class, which is the base class for all data types in C#.