From Mac Guides
Activity Monitor (named Process Viewer prior to Panther) is an application included with Mac OS X that can be used to view running processes and other system information. It is located at /Applications/Utilities/Activity Monitor. Much of what it does can be easily done in Terminal, however it provides a graphical interface which most find easier to use.
Activity Monitor can be used for the following tasks related to running processes:
- Viewing a list of all running processes, including background processes
- Viewing which processes are using a large amount of processing power or memory
- Killing (quitting or force quitting) running processes (especially useful for background applications)
- Viewing information about a particular process
It can also be used to find the following system information:
- CPU usage statistics and graphs
- Memory usage statistics
- Disk activity and usage information
- Network activity
There are several ways to configure Activity Monitor to show easily viewable information about system information mentioned above.
- It can be configured to show a floating CPU meter in the Window > Show Floating CPU Window submenu
- Its Dock icon can be configured to show various meters in the View > Dock Icon submenu