DIP Nat screenos to Junos

Hi,

I just need to understand  so if someone can explain will appriciate.

set interface aggregate1.109 dip 6 41.79.xxx.xxx 41.79.xxx.xxx

VS.

set interface aggregate1.109 ext ip 41.79.xxx.xxx 255.255.255.224 dip 5 41.79.xxx.xxx 41.79.xxx.xxx

What makes the dip5 defrent from dip6. I understand dip6 is a source based nat with a pool and so is dip 5, but what is the ext ip portion. Just trying to understand what it would mean in junos terms.