Network Interface Card. The card between your computer and the network ;)
should show you all currently installed and detected interface cards in your UBO. If not, try to find it by scrolling through dmesg
dmesg | less -XF
mii-tool will provide more information about your NIC:
# mii-tool eth0: negotiated 100baseTx-FD flow-control, link ok
in this above case it shows I'm using 100baseT full duplex and the link is OK.