collections in java

tell me briefly about collections in java . how to use that in real time scenerio

A collection (sometimes called a container) is an object that groups multiple elements into 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 an order (a collection of order lines), a mail folder (a collection of messages), or a telephone directory (a collection of name/phone-number pairs).