Hi

Loopback interface is a logical interface which is mainly required to maintain routing protocol neighborship alive though your physical link goes down.

It comes into effect when you have multiple links terminated and also in scenarios like where you need a router to create neighborship with the loopback ip address which wont go down at any point of time.

it can be used to form your ipsec tunnels also especially when you have multiple links connected to that location.

By doing so the ipsec tunnel remains up since it can be reached via different physical links though one of the link is down.

Distribute lists are used to filter networks received in updates and to suppress networks from being advertised in updates.

http://www.cisco.com/en/US/partner/docs/ios/11_2/np1/command/reference/5riprout.html#wp2471

http://www.cisco.com/en/US/partner/docs/ios/11_2/np1/command/reference/5riprout.html#wp2518

do refer the above links for more info.

regds