Some respond to fingers and some seem to respond to pens and I am just wondering what are the different types?
There are resistive, surface acoustic, capacitive, infrared, optical, strain gauge, dispersive, and the new bidirectional. Wiki has a great article on it.
If I could ask a related question: when the iPhone was first announced, Jobs made a big deal about “this time we patented everything!” but of course there are a whole bunch of touchscreen phones coming out now from other companies. How did they get around Apple’s patents? And if it was that easy to come out with similar technology, what was the point of making a big deal out of the patents in the first place?
Interesting Wiki article. I know about a few of the systems, but not the others.
Does anyone know which technology the iPhone uses?
The iPhone uses a capacitive touchscreen, but an unusual one - there’s a description here:
Thanks! 
My Touchsmart responds to both
But each type works better when the other is switched off.
(You can switch both on, so it will work with fingers and the stylus, but the using the… oh I can’t be arsed to finish this.