What are collections in java?

Defining Collection

A Collection allows a group of objects to be treated as a single unit.
Collections are used to store, retrieve and manipulate data, and to transmit data from one method to another. Collections typically represent data items that form a natural group, like a poker hand (a collection of cards), a mail folder (a collection of letters), or a telephone directory (a collection of name-to-phone-number mappings).

"Collection" word usage

The overall term for Java's data structure facilities is Collections, a term is is an alternative to the more common Data Structures. In addition to describing general data structure facilities, java.util.Collection is the name of an interface and java.util.Collections is the name of a class containing many data structure utility methods. Three different names would have been better.