The following information can also be found in the help section of Outlook.
Microsoft Outlook makes it possible for you to give another person access to your Inbox and any other Outlook folder you want. The process of granting someone permission to open your folders, read and create items, and respond to requests for you is called 'delegate' access.
(Delegate: Someone granted permission to open another person's folders, create items, and respond to requests for that person. The person granting delegate permission determines the folders the delegate can access and the changes the delegate can make.)
See also: How do I set up delegates in Outlook?