New to XSLT, XML, DOM etc.???

hi all,
(XSLT, DOM, SAX)
I m new to all these terms. Can u pls guide me to start off. What are these terms? Why do we need them? What are the advantages of DOM over simple style sheets of HTML? What are templates? How to create and use them? any links for Templates creation/documentation? 
If possible please forward sample template creation code... and how to use it....

hope u all will reply....

thanx in advance,
cheers
Kets