Outlook 2011 replaces Entourage as the standard Microsoft Office mail program on the Mac. It is intended to be (and is) very similar to Outlook 2010 on the PC, with a few notable differences. If you are a former Entourage user, however, you will notice some big changes and some key omissions.
Like its Windows counterpart, Outlook 2011's user interface is dominated by the ribbon, a strip of text and icons across the top of the window that is meant to make finding features easier. There are three tabs in Outlook's ribbon. The Home tab is where you will find the things you need most frequently, like composing a new email or replying to an existing one.
If you are a former Entourage user, here are some important differences:
These changes are cited from this Macworld article.