The “interface name” part of an ifconfig command can be a simple interface name, such as eri0, bge0 and such, or a logical unit such as eri0:1, eri0:2 and so on.
This makes it easy to setup more than 1 ip address on a network card, and hence to make virtual servers.
Hmm good to see you are also trying to have an alternative knowledge base 😉