What's the difference between kill and killall

Question

The difference between kill and killall

I tried kill command as

$ kill "PDF Expert"
-bash: kill: PDF Expert: arguments must be process or job IDs

It report error,
However, when test with

$ killall "PDF Expert"

The application "PDF Expert" was closed.

What's the difference between them?

Answer 1

kill works by process ID but killall can determine the process ID by process name. If you give the process name instead of the process ID, killall might find the process ID and kill it.