Outlook Web App originally called Outlook Web Access and
before that Exchange Web Connect is a webmail service of Microsoft Exchange
Server 5.0 and later. Outlook Web App comes as a part of Microsoft Exchange
Server or Microsoft Office 365.
Outlook Web App is used to access e-mail calendars, contacts,
tasks, documents and other mailbox content when access to the Microsoft Outlook
desktop application is unavailable. In the Exchange 2007 release, OWA also
offers read-only access to documents stored in Microsoft SharePoint sites and
network shares. Microsoft provides Outlook Web App as part of Exchange Server
to allow users to connect remotely via a web browser. Some of the functionality
in Outlook is also available in this web "look-alike". The most
important difference is that Microsoft Outlook allows users to work with
e-mail, calendars, etc., even when an internet connection is unavailable,
whereas OWA requires an internet connection to function.