Load average tells you whether work is queuing on the machine, but by itself it does not say why. A step-by-step routine turns a vague "slow server" into a CPU, memory, disk or I/O problem. Use it in incidents and in scenario interviews such as "load is 8 on a 4-core box". Do not assume high load means high CPU; waiting on disk or NFS raises it too, and more cores will not fix that.