ipv6 tunnel

[Tesi TLC (G. MazzinI)]

Hello ! 
We are two students of Italian University
We use linux RedHat 5.2 kernel 2.1.126 with modutils 2.1.121.
We would to install ipv6 on our linux machine.
We are using the Bieriger's HOWTO !    
We compiled :
inet6-apps0.34 
telnet95.10.23.....
libcap0.4a6......
tcpdump3.4a....
traceroute1.4a5....
net-tools1.50
chimera2.0a14....
......................

We don't understand tunnel ipv6 !
Where can we get some information ?
We would like to know how to configure ipv6 tunnel !
We don't understand why we must set up sit0 and sit1 !
Anybody can help us ? 

Thanks

Luca & Giancarlo