The macOS has contained the Activity Monitor App in the Utilities folder for quite some time. I think people tend to overlook this informative App when doing troubleshooting on their Mac, but it can help in diagnosing problems. It can also just show you what certain processes are doing on your Mac if you are curious. This article covers just about everything you can do and check with the Activity Monitor App. Even if you are familiar with Activity Monitor, you may learn something new in the article, it is very granular.