Extraído de la página oficial de Shorewall firewall

Netfilter – the packet filter facility built into the 2.4 and later Linux kernels.
ipchains – the packet filter facility built into the 2.2 Linux kernels. Also the name of the utility program used to configure and control that facility. Netfilter can be used in ipchains compatibility mode.
iptables – the utility program used to configure and control Netfilter. The term ‘iptables’ is often used to refer to the combination of iptables+Netfilter (with Netfilter not in ipchains compatibility mode).