Those are the max speeds that each standard is capable of (10mbps= Ethernet, 100 is Fast Ethernet), and normally you can get close but not quite to that.
Another factor is HOW you connect the pcs: a hub shares the bandwidth, so 4 rigs on a hub may be slower if all are trying to communicate. Switches use dedicated bandwidth, so each computer can get up to the max. Hubs and switches are usually 10/100 nowadays, but a few years back many of them were only one or the other.
I have never used a patch cable to hook 2 computers directly together but I would expect them to be able to use all the bandwidth as well.
The last determining factors in speed are distance and cable quality: the further away the pcs are, the more likely they are to drop packets and need to send them again. Cat5 (regular ethernet cable) is good for 100 meters as I recall..........about 320 feet or so.