WAN interface card(WIC) slots
Two fixed WIC slots are present in 2600 series router except 2691. It has contained 3 WIC slots.
Network Module Expansion Slot( NM) slot
The purpose of this slot for installing the Network module either WAN or LAN
LAN0/LAN1
These are build in integrated LAN controllers in Motherboard. There are three types such as Ehternet, Fast Ethernet and Token ring