What is the difference in touching the screen of Galaxy Tab (10.1) with Finger and the S Pen ?
When using the S-Pen your Touch is a bit more accurate, if you use a app like "Papyrus" where you can write on a "Virtual" Sheet of Paper you will see that a Pen is much more accurate. But in normal Terms if you dont need to be that accurate your Finger is enough.
The Pen is nothing more than a Piece of Hardware having a organic material on it's top. That the Galaxy Tab can recognize.