What are the interface prefix meanings in ifconfig?

From the ASUS RT-N56U wiki page:

What are the existing network interfaces (transcript naming interfaces)?

    br0 = LAN + WLAN + AP-Client + WDS
    eth2 = Ethernet interface GMAC1, that connected to the switch (trunk port).
    eth2.1 = LAN (VLAN VID1)
    eth2.2 = WAN (VLAN VID2)
    ra0 = WLAN 5GHz
    ra1 = WLAN 5GHz Guest
    rai0 = WLAN 2.4GHz
    rai1 = WLAN 2.4GHz Guest
    apcli0 = AP-Client 5GHz
    apclii0 = AP-Client 2.4GHz
    wds0-wds3 = WDS 5GHz
    wdsi0-wdsi3 = WDS 2.4GHz 

In the no-VLAN firmware

    eth2 = LAN
    eth3 = WAN 

They mean whatever the driver designer wanted them to mean. There are many many others too, like ib0 for Infiband devices. But I am not aware of anywhere that has a complete list as again it depends on who develops the driver as to what the name of the device is. Usually it gives some clue as to the type of board but that is about it. The number after the device designation is generally used to indicate which of several ports/devices the device is.

You can see all interfaces using ifconfig -a or ip address show; It will show them even they are down.