I'm doing a comparison about Windows OS and Ubuntu OS, and I know there is a "system monitor" in Ubuntu, can i know how it works and what is the function of it?
There are many system monitors in Ubuntu, but the one that is installed by default, is the Gnome System Monitor. It will show you system processes, resource use (CPU, memory, network) and mounted filesystems and their use.
gnome-system-monitor is preinstalled with Ubuntu. To open it, run
in the terminal ( Ctrl+Alt+T to run), or press Alt+F2 and search for system monitor.
(taken from here)