The load average numbers give the average number of jobs in the run queue over the last 1, 5, and 15 minutes. (These three time periods may vary from one vendor's Unix system to another, but are usually 1, 5 and 15 minutes.) In other words, the n-minute load average is the number of processes competing for the attention of the CPU(s) at any moment, averaged over n minutes.
The load average plotted here is the 15-minute average. The lowest possible load average is zero, the highest unlimited, though we rarely see load averages exceeding 20, and even 10 is unusual. A load average of one or two is about typical.
