...where is the address book in Apple Mail. I have ceased with Entourage, having upgraded the computer and now wish to use Mail, but how do I build an address book, I can't find it and I have all my email addys to add.
Yup the brown book is your address book, mail uses some database within the OS to read data from that address book library. Which will come up as you type in names etc "dad" will come up and will suggest emails you have under "dad"
Also take a look at the Applications folder (while Finder is active, either click the "Applications" shortcut in the Sidebar, or press CMD+SHIFT+A, or go to Menu Bar > Go > Applications) to see, what applications you have.
There is also an Applications folder shortcut in the Dock, on the right side of the Dock separator.
And then also have a look at the following to learn more about Mac OS X: