Difference between ipf/ipfw and ipnat/natd

[Andreas Dahlén]

Hello!

I'm going to install FreeBSD 4.8 as a firewall/gateway for my homenetwork.

I've seen that there are two implementations of firewalls in FreeBSD; 
ipf and ipfw and fot NAT ipnat/natd.

As I understand ipf and ipnat works together and ipfw and natd. Is that 
correct?

Which one of them should I use?
Is there some major differences between them?

/Andreas