a contact list is an address book, but an address book is a contact list that can be used as an address book - it's different terms for what is essentially the same thing (at least from my perspective)

your contacts have additional information, phone numbers and postal addresses etc... as well as email addresses - by default local outlook contacts are not available to be used as an address book - the steps outlined by DarkGuardian and myself allow you to use your local contacts as an address book. otherwise, you may find that you can easily email internal users, but have to rely on either the NK2 file (history of entered addresses) or manually typing each email address when sending to external recipients.