Activity Monitor

Activity Monitor is a utility from Apple that is included with macOS. It was previously called ProcessViewer in early versions of Mac OS X

Functionality
Activity Monitor measures how resources are being used by different applications (or background processes) on a Macintosh. This can be used to monitor the Mac's processor and disk activity, as well as the memory usage and network activity. Using this utility can be useful to inspect which individual processes are drawing heavily on the Mac's resources, such as graphics, video editing, or even a complex web page. There are options to filter what is listed, and the process list can also be saved and be exported. Finally, there is an option to quit or force quit an application (unresponsive processes are displayed in red).

CPU, System Memory, Disk Activity, Disk Usage and Network usage can be viewed in the tabbed lower part of the window, where the activity is presented in a real-time chart as dotted bar graphs. If needed, the Dock icon can be switched to keep an eye on the specific usage.

Location

 * Startup drive > Applications > Utilities > Activity Monitor