Dual gigabit ethernet+lan'ing

hey there   ,

i'l b getting a new rig wid dual gigabit Ethernet lan and i was thinking of networking with my old rig as well as my brother in laws (he lives a floor below me).

i don't quite understand what sort of features the dual gigabit lan can do..that being sed - how can i network the other two pc's with mine and is it necessary to buy a router or a switch?

the networking is only for File transfer and Lan Gaming, not internet usage.

Any help is appreciated!

Thanx