htop
This is htop, a cross-platform interactive process viewer. It is a text-mode application (for console or X terminals) and requires ncurses.
I personally use htop to find out what processes are running on my system and to kill them if necessary. It’s also provide good information about the system load and memory usage, you can sort the processes by CPU or memory usage, and you can filter the processes.
Keyboard bindings
Toggle tree view::t
Search::/