FAQ: lan_ifnames vs lan_ifname

[supremedalek]

I am feeling stupid but this is Saturday. So, what is lan_ifnames used for and what is the difference between it and lan_ifname? In my wrt54g I saw them being used as

Code:

lan_ifnames= vlan0 eth2 eth3
lan_ifname= vlan0

I can understand the lan_ifname (I create vlan0 and defined the ports associated with it), but what is lan_ifnames doing there? I thought eth2 went straight to the wifi. Who is eth3? Am I missing something here?