Many people aren’t aware of this beautiful feature introduced with Windows 2000 and continuing in it’s successors. To get a better sense of what it is, lets a take a example. Your CPU is spiking to 100% at mid nights and you got the task of identifying the root cause. The spike is very sporadic in nature and lasts for very short time. How will you deal with this situation to see which process is taking high CPU?. Here comes the benefit of WMI event notifications. You can trigger a monitoring in your system using WMI event notifications to monitor the CPU utilization and do a process dump when it touches the monitored value. Task is done and you don’t need to spend time in monitoring manually. This is just a example only and you can adopt this to get alerted when a process starts or ends.
I may not be good at explaining the real use of WMI event notifications but I have found beautiful blog entry which explained this in detailed. Read it to become smart administrator.
You can also refer to Microsoft Technet Site Article