This is htop, an interactive process viewer for Linux. It is a text-mode application (for console or X terminals) and requires ncurses. Tested with Linux 2.4 and 2.6.
Comparison between htop and top
* In 'htop' you can scroll the list vertically and horizontally to see all processes and complete command lines.
* In 'top' you are subject to a delay for each unassigned key you press (especially annoying when multi-key escape sequences are triggered by accident).
* 'htop' starts faster ('top' seems to collect data for a while before displaying anything).
* In 'htop' you don't need to type the process number to kill a process, in 'top' you do.
* In 'htop' you don't need to type the process number or the priority value to renice a process, in 'top' you do.
* 'htop' supports mouse operation, 'top' doesn't
* 'top' is older, hence, more used and tested.