There is a simple rule that you can apply.
If you can navigate the screen with your finger, then it is a capacitive screen, which means it is compatible with a "capacitive" stylus.
Capacitive Styluses usually have rubber or foam ends that are soft.
The Wikipedia page on the subject is located at: http://en.wikipedia.org/wiki/Capacitive_touchscreen#Capacitive
For example pictures, check out http://www.stylusshop.us
(Most styluses on there are "capacitive")
If on the other hand you cannot navigate the screen with your finger, but have to use a small and hard plastic tip, then is is considered to be a "resistive stylus" . Those are getting phased out more and more.
Examples of those include the Stylus for the old Palm Pilot or the Stylus that comes with the new Nintendo DS
The Wikipedia page on resistive screens can be found at: http://en.wikipedia.org/wiki/Touchscreen#Resistive
An example of a modern Resistive tip is here: http://www.stylusshop.us/products/multi-tip-touch-stylus
Hope it helps