Last Updated: Aug 13,2010
Assuming you're asking about Microsoft Exchange. Does a bunch of stuff but mostly used for corporate email via Microsoft Outlook as far as I've ever seen.
"Microsoft Exchange Server is the server side of a client–server, collaborative application product developed by Microsoft. It is part of the Microsoft Servers line of server products and is used by enterprises using Microsoft infrastructure solutions. Exchange's major features consist of electronic mail, calendaring, contacts and tasks; support for mobile and web-based access to information; and support for data storage."
Microsoft Exchange Server - Wikipedia, the free encyclopedia
It's basically Microsoft's version of MobileMe in that it acts as a cloud based service to sync information such as contacts, calendar, and email.
Let me google that for you
Separate names with a comma.