NAT device explanation

Hello all,

I am trying to understand how NAT mode works and i have a question.

I  know that via DHCP the host always takes .1 IP address and the quest takes from .128 and on.

I know how NAT works. I would expect that the quest should have as Default gateway the host (.1). The packets arriving would be NATed to the physical NIC of the host and reach the outer world.

I see though that the quest has DG= .2 (referred as the "NAT device" by VM guides). What is that? Why should you insert .2 in the middle? And how does it work?

Thanks!