Can someone please tell me, what is the difference between PPPoE Pass-through and Bridge Mode. They both sound the same. This is on a 2710n.

Thanks

pppoe pass through does all the authentication plus some other tasks sending them to the router
it also use the public ip of your isp and send to router private ip ... that can cause double nat (sometimes this can cause issues to post forward or firewalls etc)

Bridge mode only allow some packages to be send at the other router and is less complicated if someone is not expert
This is the best way to connect your modem to a separate router

see here
http://www.techlineinfo.com/difference-between-pppoe-and-bridge-mode-of-adsl-modem/