Yes, exactly. The command kill sends a signal to a (exactly one) process, identified by the given process ID. Issue a

Code:

kill -l

to see a list of signals your system is able to send. killall, on the other hand, works on groups of processes: it will send the same signal (if i remember correctly signal 9) to all processes identified by a common command. You can try the difference with a little experiment: Issue the command

Code:

sleep 1000 &

three times. In the ps -er | grep sleep output you will see three times the same process "name" (in fact the command, as processes have no names, just IDs) but with three different PIDs, like this:

Code:

$ ps -fe | grep [s]leep
bakunin      5897  5893  0 21:12 pts/0    00:00:00 sleep 1000
bakunin      5898  5893  0 21:12 pts/0    00:00:00 sleep 1000
bakunin      5899  5893  0 21:12 pts/0    00:00:00 sleep 1000

You can terminate each one of them by kill -15 <PID>, but killall sleep will first search for all processes with a command "sleep", find these three and then send one after the other a signal.

Web browsers traditionally wreak havoc in the process model for reasons i have not fully figured out. I.e. it is not possible to start a Firefox (or Chrome, for that matter) two times, like any other program. And each window (i hate tabs, so my browser instances are all windows) is not a separate process but - honestly, i have given up on trying to understand. I all programs would behave that way i'd already asked for a permanent place in the asylum. Why a process started once has two processes instead of one i don't understand. If you are interested - and i hope you are, because this is what makes you learn more and more - i suggest you investigate and tell us if you find out. I don't have this xdotool you are using.

I hope this helps.

bakunin