asterisk users - Feb 2007 - Packek2Packet Bridging vs. Native Bridging

I am just wondering if someone can explain the difference between
Packek2Packet Bridging vs. Native Bridging in Asterisk.

I'm basically tyring to make sure the media travels end-to-end and
I've see both of these bridging types mentioned on the asterisk
console.

Regards,
David