There are usually three kill commands in most of the linux distributions: `kill`, `pkill`, `killall`.
They are all used to send a signal to one or more processes.
The main distinction is how they choose the processes they are going to send a signal to.
kill: sends a signal to the process given by its process id (PID)
$ sleep 100 &  13793 $ kill 13793
killall: sends a signal to all processes matching the given name
$ sleep 50 &  19194 $ sleep 100 &  19196 $ killall sleep - Terminated sleep 50 + Terminated sleep 100
pkill: sends a signal to processes matched by the given regular expression pattern
$ sleep 100 &  19277 $ ./sleep.sh &  19282 $ pkill sleep - Terminated sleep 100 + Terminated ./sleep.sh