For example, you can store notes about when and where you met a person in plain text.  In my address book I have an entry called "Airline Frequent Flyer Numbers" and within the Notes section I have placed the numbers for the airlines I like to fly.  It's a great way for me to store the information in a single place as each airline has a unique name for their particular program.

The following example shows the default Address Book carf for Apple Computer.  Note the following for the card:

• Name
• Photo
• Phone Number
• home page
• address
• Note
• Updated date in the lower right corner
  

Address Book integrates with several Mac OS X applications such as Mail, iChat, iCal.  Externally, Address Book can interoperate with Apple's .Mac service and synch with Bluetooth devices.  Address Book is built using the industry standard vCard format.