And that prompts another question? How's that done? Outlook 2011 has no sync capabilities and when I installed that preview version of the new Office that Outlook didn't have it either.
Office 365 also provides access to a hosted-in-the-cloud exchange server, that is what the client software talks to for exchange email and exchange calendar. Multiple Office for Mac and Outlook for Mac clients can access that exchange email and calendar. IOS calendar and mail can access the exchange calendar and mail services. Sync of exchange mail and calendar between devices happens via the hosted exchange service.
Outlook can also access IMAP accounts (where "sync" happens via each client accessing the IMAP server).
If you have standalone Office for Mac 2011 (say bought previously), you need access to an exchange environment for exchange email and calendar, otherwise its an expensive IMAP mail client. Office 365 provides both the exchange server and client software.
Hope that helps.