System monitoring is one of the major tasks of system administration. Various tools are available for doing simple monitoring: top, ps, free, vmstat, netstat, iostat, and mpstat.
An all-in-one GUI tool to monitor system status is GTop. To run GTop, select GTop System Monitor from Utilities sub-menu of Programs menu on Panel. You can also start it from command line: type gtop. Please note that all tools have limitation, especially GUI tools. It is because of the complexity of GUI tool design.
Using GTop, you can check statistics of Processes, Memory usage and Filesystems. The tabs above the color bars allows you to switch among the various type of statistics. The color bars tells you the current CPU usages, and memory usage. The status bar at the bottom gives you figures of the system's uptime and CPU usage.
In Processes statistics mode, the buttons below the color bars allows you to sort the statistics. For example, clicking on the MEM button, the sorted order of the processes according to memory size consumption are toggled.
The Memory Usage statistics mode gives you a graphical view of the memory usage of various processes. Processes having small footprints are grouped together.
The Filesystem statistics mode gives you a graphical view of the filesystem usage.
To fine tune the statistics display, you can alter the default values by going to the Preferences... option in the Settings menu. Unless you know what you are doing, do not alter the values.