Actuallly, twisted DOES mean that they;re physically twisted. The phrase is UTP and STP - Unshielded Twisted Pair and Shielded Twisted Pair respectively. Each cable has four pairs of wires, and each pair is twisted together (thus cancelling oput mushg of the noise on the line). The Unshielded has nothing covering this group of wires except for a PVC coating. The STP cable has a foil coating that custs down external interference even more. This is generally only used where interference could be a problem (i.e. if you're running Cat5 cable in the same trunking as mains cable or other electromagnetic noise-producing sources).
You should never need STP cable in a normal domestic situaltion unless this is the case. To connect an Xbox and PC directly, you'll need a crossover cable, but to join them via a hub or router, you can use standard straight-through cables.
If you're interested, to make up a cross over, you just need to swap over pins 1 and 3 and 2 and 6 on the one (and ONLY one) end of the cable.
Thus:-
(numbers are pins - looking at the bottom (pin side) of the plug, they're numbered 1 to 6 from left to right.)
1 ------------------------------------------ 3
2 ------------------------------------------ 6
3 ------------------------------------------ 1
4 ------------------------------------------ 4
5 ------------------------------------------ 5
6 ------------------------------------------ 2
a normal cable would just be the same at both ends.
Hope that helps.
Squidge : The distance is max 100m max on both for standard Cat5e cable before any signal drop-off - more than enough for most people.