What is a Petri Net ? I think a good reference to answer this question is the wikipedia link
Which type of PetriNet's is used inside the CS-Framework ? The CSPNPetriNets are based on the nets, developed by Dr. Bernd Baumgarten. In his Script you can find the exact definition. Script Baumgarten If that link does not work, use this one, to Dr. Baumgarten's homepage.
Were i can find more documentation about Petrinet's ?
On the Homepage of Dr. Baumgarten, some further examples and exercises are collected
The book from Dr. Baumgarten, called "Petri-Netze. Grundlagen und Anwendungen" ISBN-10: 341114291X ISBN-13: 978-3411142910