Bus

The paths in a computer that devices use to comunicate are refered to as buses. For example the link between the CPU and RAM is the Front Side Bus (FSB). USB devices communicate over the Universal Serial Bus.

If you think of a computer as a country and its various components as cities and towns, then a computer's buses act like the roads and interstates that would connect them. Some pieces, such as the processor and RAM have to "talk" to one another a lot, and so require a very large, thick, interstate-sized bus (the FSB). Other, less frequently used components, such as your ethernet card or USB devices require a much thinner bus.

The "width" of a bus can sometimes effect the speed of your machine, just as too many cars on a small road causes a traffic jam. Thus, computer companies are always coming out with new component standards that support higher bus speeds, and thus more throughput. In the RAM world, the more recent DDR2 spec has a much higher bus speed than the older DDR. Intel processors are moving away from the old 800 Mhz FSB to a faster 1066 MHz speed. Also, the USB standard recently upgraded from USB 1.1 to USB 2.0 (which is roughly 50 times faster). This is simply a product of the market's neverending drive to surpass itself - if you're buying a new computer, try to get the more modern stuff, but otherwise don't worry too much about it.