Need some explanations plz help!

Outlook and Outlook Express are programs that you run on your computer.
Outlook Express is a basic email client included free with internet explorer.
Outlook is part of the office suite. It has more functionality such as Calendar and Tasks, and the ability to import and export.
Exchange on the other hand is a centralised email system designed for corporate messaging. Usually outlook is used as the client to access an exchange email system.
There is lots of product information on the Microsoft web site which will tell you all about the features, advantages and benefits of each.

thx alot for your answer , it was really helpful

antoher difference between outlook and outlook express is in express you have an integrated newsreader, which in outlook you don't have.