Outlook 2011 Help and Support
Sharing and Delegating
When you share your calendar with other Outlook users, they have access to your calendars but not meeting related emails that are sent to you. You can allow others to create meetings on your behalf and make other changes to your Calendar when you share it, but you will be responsible for accepting and declining meetings.
Delegation is allowing other Outlook users to act on your behalf, by doing such things as receiving and responding to meeting requests or sending email messages for you. The person granted this permission is called a delegate and you can grant them limited permissions or up to full control over items in your mailbox and calendar.