iPhone has loads of functions that you will be probably more used to seeing on your home computer, or which the following are just a few:

Camera
iPhone has a built in camera comparable to the camera in many of the latest good mobile phones
Calendar
An organiser with list of upcoming events, reminders etc
Calculator
Does what it says on the tin!
Stocks and Shares
Latest figures from the city so you can chart the progress of your financial assets
Weather
Latest updates in your area
Clock
With alrm function and stop watch
Notes
Text editor

Unfortunatly the iPhone cannot send MMS messages (like SMS messages but with attached multimedia e.g image attachment)
Sadly, there is no instant messaging programme on the iPhone.