Setting an FSB speed is related directly to the speed grade of memory a system must use. The memory bus connects the northbridge and RAM, just as the front-side bus connects the CPU and northbridge. Often, these two buses must operate at the same frequency.
Frequency refers to the number of occurrences of a periodic event per time and is measured in cycles/second. In this case, there is 1 cycle per 2 seconds. So the frequency is 1 cycles/2 s = 0.5 Hz. 6.
At its most basic, frequency is the number of times an event happens during a time period. For example, the frequency of Christmas is once per year. In science and nature, waves carry energy and have frequencies. Sound and light are waves as real as the ones you find in the ocean.