1 or 2 nic's

[lem <lem health pchrd dost gov ph>]

can anyone tell me if it's better to place 1 or 2 nic's in a host.
one nic connects to the internet (actually a hub  connected to another
network which is connected to the internet) and another nic for the
internal network.
I'm wondering what this method is called. Oviously i'm new to networking.
sorry....
can anyone also suggest reading materials... sorry again...

---lem