Microsoft Exchange Information Store is a storage platform that is used to manage numerous types of information within an Exchange Server deployment.
Introduced in Exchange 2000, the Exchange Information Store, also known simply as the "Exchange store," is primarily comprised of mailbox and public folder databases in the Exchange 2010 version, though in past versions storage groups and transaction logs have played a large part as well.
Mailbox databases contain data for individual mailboxes and their contents. Public folder databases contain all the data that make up public folders in a particular Exchange setup. The Information Store is effectively managed by manipulating each of these core components.
The Exchange Information Store was discontinued in Exchange 2013 in favor of the Managed Store.